I only need answers for B and C, or atleast how to solve! Please help! Fake answers or bots will be reported

Agrocery store has 12 lb of trail mix that is 10% banana chips. the store's manager would like to add banana chips to bring the new mix up to 25% banana chips. write and solve a system of equations to find out how many pounds of banana chips manager needs to add.

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)

Write an equation for the function that includes the points (1,4/5) and (2,2/3)