Find the value of x if a triangle measures 65, x, x-5

Can someone me and do the problem plz so i can understand it more better

If jaime wants to find 60% of 320, which table should he use?

Sanjay solved the equation below. which property did he use to determine that 7x+42=42 is equivalent to 7(x+6)=42 7x+42=42 7x=0 x=0