Derek has $20 to spend on used books. hardcover books cost $5 each and paperbacks cost $2 each. complete the equation which determines the number x of hardcover books and the number y of paperback books he can buy.

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

well there are two answers for that.

1: you need 120 ones then that will equal up to 120.

2: you could also do one 100 and 2 tens.

those are the answers that i have thought of.

this is answer of 144 cubic meters

27 +27 or 27times 2=54

the diffrence is 0