I have been trying to figure out the answer to this question but I keep getting 3 square root of 3. I need some help.

Find the solution of this system of equation -7x+y=-20 9x-3y=36

An investment decreases in value by 30% in the first year and decreases by 40% in the second year. what is the percent decrease in percentage in the investment after two years

With both problems. a.s.a.p directions on photo ^