B. Is the correct answer. For part B, he can buy 15 balloons since X=15. Plug this back into the equation to check: 2(15)+20=50.
2(15)=30+20=50.
Since it is parallel, gradient must be the same so it will be 1/2
y=1/2x+c
-7=1/2(0)+c
c=-7
equation is y=1/2x-7
A = 2•3.14•3•8 + 2•3.14•3^2 = 207.34512
