7. using k as the constant of proportionality, write an equation that expresses: z varies jointly as x and y. if z = 24 when x = 3 and y = 4, find z when x = 5 and y = 6. (show steps)

60

Step-by-step explanation:

"z varies jointly as x and y" can be expressed algebraically as z = kxy, where k is the constant of proportionality.

Given:  z = 24 when x = 3 and y = 4, then 24 = k(3)(4), or 24 = 12k.

The const. of prop. must then be k = 2.

So now we have the specific relationship z = 2xy.

If x = 5 and y = 6, then z = 2(5)(6) = 60.

step by step explanation: when u removing the parentheses and combined them that would be : x+3y-x-y=2y