How to solve this equation

Set up an equation for each store by multiplying the cost of the basketball by the number of basketballs bought (b) and add the cost of the hoop:

Hoops House: total = 20b + 200

Baller Basement: total = 15b + 250

Now to solve for b, set the two equations equal to each other:

20b + 200 = 15b + 250

Subtract 15b from both sides:

5b + 200 = 250

Subtract 200 from both sides:

5b = 50

Divide both sides by 5:

B = 10

The answer is 10 basketballs

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer