Help please (pics below)

How can you decide witch operations to use to slice a two step equation

If x + 10 = 70, what is x? a. 40 b. 50 c. 60 d. 70 e. 80

1. writing an equation for an exponential function by 2. a piece of paper that is 0.6 millimeter thick is folded. write an equation for the thickness t of the paper in millimeters as a function of the number n of folds. the equation is t(n)= 3. enter an equation for the function that includes the points. (-2, 2/5) and (-1,2)