Okay. The question is m/9 - 17 = 21. First off, we will add 17 to both sides. -17 + 17 cancels out. 21 + 17 is 38. That leaves m/9 = 38. Multiply each side by 9 to isolate the m, because m is the numerator and 9 is the denominator. m/9 * 9/1 cancels out. 38 * 9 is 342. Let's check this. 342/9 is 38. 38 - 17 is 21. 21 = 21. There. x = 342.
The answer is 5/4 or 1 and 1/4 (both answers are correct just different forms), hope this helps !