Remember the formula for calculating volume is: Volume = Area by height. V = A X h.
For a triangle the area is calculated using the formula: Area = half of base by altitude. A = 0.5 X b X a.
So to calculate the volume of a triangular prism, the formula is: V = 0.5 X b X a X h
Start with

Subtract 15 from both sides:

Divide both sides by 2a:

F(x)=x/(3x+2)
f(a+h)=(a+h)/(3a+3h+2)
Make the numbers in numerical order, then subtract the greatest number by the least