Jack paid $64 for two algebra and three geometry books. he paid $66 for three algebra and two geometry books. what is the cost of each book?

Lets make the cost of the algebra textbook = x and the cost of the geometry book = y

2x+3y=64

4x+2y=66

now we get one of these equations in terms of one variable

2x+3y=64 - - - > 2x=64-3y - - - > x=32-1.5y

now we can plug that numeric value back into the other equation

4 (32-1.5y) + 2y=66

we can now simplify this equation in order to get the value of y

4 (32-1.5y) + 2y=66 - - - > 128-6y+2y=66 - - - > 128-4y=66 - - - > - 4y=-64 - - - > y=16