What is 35/21 in lowest terms?

to simplify the fraction you must first find the number that goes into both numbers, in which is 7;

So divide both the numerator and the denominator by 7;

35 : 7 = 5

21 : 7 = 3

So your final answer would be;

35/21 = 5/3 = 1 2/3 (in simplest form)