21) Choose √7^2+3^2 and solve for c.(You can use the calculator).
22) The minimum possible length could have been 39.5
23)Using the formula g/cm^3 Divide 150 by 100 which gives you 1.5. So the density of the apple is 1.5g/cm^3
I'm sorry I don't know the last two but you can do these ones for now.