Finding denominators of equivalent fractions quiz. Equivalent fractions are two fractions which if reduced to the lowest terms result to the same fraction value. The same applies if they are converted to decimals or fractions. In solving this problem, notions of pre-algebra come in handy. Replace the missing fraction with a variable like ‘x’ for example. Then cross-multiply and make ‘x’ the subject of the formula. Replace the value of ‘x’ in the equation and simplify the equation to the lowest terms to find out the values on both sides of the equation are the same. Fractions exercise for 3rd, 4th, 5th and 6th grade students.