Plz help me on this I dont understand how to do it. B.) SUBSTITUTION METHOD

1) 2x + 8y = 20 2) x = 5
y = 2 2x + y = 10

The monetary value earned for selling goods or services to customers is called a.) revenue b.) assets c.) money d.) accounting

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

Suppose that sahil knows that 45 people with ages of 18 to 29 voted. without using a calculator, he quickly says then 135 people with ages of 30to 49 voted. is he correct? how might sohil have come up with his answer so quickly?