Hi again Natalie
We have 7/8 x = 21
All you have to do is cross multiplication
7 * x = 8*21
7x = 168
x= 168/7
x= 24
I hope that's help:)
Now if you want you can also check if the answer is correct
7/8 24 = 21 ( replace x by 24)
7*24 = 8*21
168 = 168
Yes the answer is correct and I hope its help:)