The sum of the digits of a certain two-digit number is 7. Reversing its digits increases the number by 9. What is the number? write a system of equation to slove the problem
A) x + y = 7 B) 10y + x = 10x + y + 9 collecting terms of equation B B) -9x + 9y = 9 multiplying A) by 9 A) 9x + 9y = 63 then adding it to equation B) B) -9x + 9y = 9 18y = 72 y = 4 x = 3
