X=3 . ok well ur gonna do reverse mathematics so start by subtracting 2 from 17 (bc the oppistite of addition is subtraction) an then rewrite the equation. 5x=15 and then divide 15 by 5 and it equals 3 and then do it all over again meaning put the equation as it was but with the value. 5x3+2=17 and it all makes sense. im so sorry i answered so late i just got this question recommended to me.