Marie invested $800 in an account that pays 10% r =.10 simple interest per year. The equation to represent Marie’s investment is A = P + Prt, where A is the value of the investment, in dollars, P is the starting principle amount, in dollars, r is the interest written as a decimal, and t is the number of years invested. How many years(t) will it before the investment is worth $1200? Then Rewrite the equation y = mx + b and solve for m.