Please give the equation and the charge for 20 hours of work

Question

For 4 hours of work, a consultant charges $400. For 5 hours of work, she charges $450. Write a point slope equation to show this , then find the amount she will charge for 20 hours of work.

Answer 1

400 = mx + b= 4m +b

450 = mx +b= 5m +b

m=50, b= 200

C(x) = 50x + 200 dollars is a slope intercept equation

point slope equation is y-400 = 50(x-4)

or y-450 = 50(x-5)

C(20) = 50(20) +200 = $1,200