Change left with him= 16x + 7x - 53 = 23x - 53 If x = 1 then the total with him is 23*1 = $ 23 which he cannot buy a toy If x = 2 then the total with him is 23*2 = $ 46 which he cannot buy a toy If x = 3 then he can buy toy and left with him $ 16, So possible answers are 16, 39 , 62, 85, ....(x+2)*23