How do you solve #5/f=35/21#?
These two are equivalent fractions. The second fraction can be derived from the first one. In order for them to be equivalent, the numerator and denominator both have to be multiplied/divided by the same number.
5 is multiplied by 7 to get 35, so f must also be multiplied by 7 to get 21.
Check the answer by plugging it into the original equation: