The number is 6 because five times 6 is 30, and 30 minus 2 is 28. You could also solve this backwards in the future and take 28 plus 2 and then divide that number by 5 (opposite of subtracting 2 is adding two, opposite of multiplying by five is dividing by 5).
5x-2=28 (writing it this way might also help, because now you just have to solve for x)