CPhill

Distance / Rate  =  Time

30 mi = 1/2 hr

2 / ( r - 8)  +  2  / ( r + 8)  =   1/2             where r is his rate in  still air

Multiply through by  2

4 / (r - 8)   + 4/(r + 8)  = 1

[4 ( r + 8) + 4(r - 8)] / [ (r -8) (r + 8)  = 1

8r   =  (r - 8) (r + 8)

8r  = r^2   -  64

r^2 - 8r  - 64  = 0

r^2  - 8r  =   64

r^2  -8r + 16  = 64 + 16

(r - 4)^2  =  80         take the positive  root

r -4 =   sqrt (80)

r =  sqrt (80) + 4  ≈    12.9 mph =   his rate in  still air 

XB =  (2808) / 2 =   1404

XR  = ( 3/5) (1404)  = 842.4

XS =  (5/8) (842.4)  =  526.5

RS  =   842.4  - 526.5  =  315.9

35 = 5 * 7

42  = 2 * 3 * 7

Smallest  is     2 * 3 * 5 * 7   =  210

n  =  210 /  35   =    6

111,111,111,111,111,111 / 9  =  12345679012345679 × 9 + 0 

111,111,111,111,111,111/ 21  = 5291005291005291 × 21 + 0

See here :  https://web2.0calc.com/questions/need-help_80318

The table shows the prices of the tickets for a charity performance 

     Type of ticket     Price per ticket

           Adult             $20

           Child              $8

1/4 of the tickets sold were adults tickets. The total amount of money collected from the sale of child tickets was $216 more than the total amount collected from the sale of adult tickets. How much money was collected from the sale of the tickets altogether?

Let x be the total sold.....so  (1/4)x =  the adult's sold  and (3/4)x = the children's sold

So

Number of adult's sold * price per ticket + 216 =  Number of chidren's sold * price per ticket

(1/4)x * 20 + 216 =  (3/4)x * 8      simplify

5x + 216 = 6x

216 =  6x - 5x

216  =  x 

Total money collected =  (1/4) (216)*20  + (3/4)(216)* 8  =  

5(216)  + 6(216)  =  

11 (216)  =

$2376

See my answer under your original post.

Let Evan's erasers at first =  E

Let Robert's at first =  (5/6)E

When Evan gives (1/2) of his to Robert he has  (1/2)E left       and Robert has (5/6)E + (1/2)E

So

(1/2)E +  50 =  (5/6)E + (1/2)E

50 =(5/6)E

50 (6/5)  = E =   60    =  what Evan had at first

The points  (0,4) and (1,1)  are on  the line

The slope of the line  = (1-4) / (1 -0) =  -3/1  = -1

Using the point  (0,4)  and the slope the  inequality is  either

y  ≤ -3x + 4   or     y ≥ -3x + 4

Note that the point (2,2)  is  in the  feasible region  and it satisfies  the second inequality

So

y ≥ -3x + 4

3x + y  - 4 ≥  0

He started on Monday  and ends on a Saturday

The first week  he earns  1 + 2 + 3 + 4 + 5 + 6 + 7 = $28

And in the  next 6 days (starting on Monday, again)  he makes   1 + 2 + 3 + 4 + 5 + 6  =  $21

$28 +$21 =   $49