for this question you can say: 1/8x = 10 so x is the answer and if u want to find the x you can multiply both sides of the equation by 8 so you will have: x = 80 and that's the number if u want to find 1/7 of 21 you should just divide 21 by 7 so you will have 3 and for the last one is same also, so the answer is 5 :))) i hope this is helpful have a nice day