CPhill

80%  =  .80  =   80  / 100   =  8 / 10    =   4 / 5

1 km  ≈ .621 miles

1 L  ≈ .264 gal

So......

28.5 km  = 28.5 *.621  ≈ 17.7 miles / .264 gal  ≈ 67.04 mpg

22 km  =  22 * .621  ≈ 13.66 miles / .264 gal  ≈  51.74 mpg

Cost for city driving  =  500 / 51.74  *  3.50  ≈  $33.82

I'm assuming that the $600 is the opening balance.....

So....the correct balance is

600  -  178.23  + 363.82   =  $785.59

3x + 2y  = 1

-9x - 6y  = 3 

Note, NSS, if we multiply the first equation by -3 we have

-9x - 6y  =  -3

Note that this system has no solution because  -9x - 6y  = 3 but it also equals - 3  .....and this is impossible....two things subtracted can't result in two different values !!!

The second answer is the correct one for the second question

(14 / 35 ) (3 / 4)   =   42 / 140  =   21 / 70   =   3 / 10  ft

5(x - 8)  = 60      divide both sides by 5

x - 8  =   12       add 8 to both sides

x  = 20

You were correct  !!!!

Hey, hectictar.....speed up those answers.....!!!!!!!

Seriously, WhichWitch  ?????

We aren't being paid for this......we try to answer as quickly as possible.....but....we can't guarantee anything.....!!!!!

(1/3) [  3      a             3                       2                      ] 

                   1          (1/3)(a + 1)       (10 + a) / 9

          _____________________________________

          3      a + 1     (10 + a) / 3        2  +  (10 + a) / 9

So

2 + (10 + a) / 9  =  4

(10 + a) / 9  =  2

(10 + a)  =  18

a  = 8

Sorry.....fixed it.....

The first graph is the correct one, NSS......

See the graph here : https://www.desmos.com/calculator/r3scah60wf