I need help on this one question

Twenty-five percent of the customers entering a grocery store between 5 p. m. and 7 p. m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.

What is the solution to the equation 9^(x+1) =27

X+y=-4 x-y=2 use elimination with adding and subtraction