How do you multiply, fractions and make sure my answer is correct

Write each fraction as an equivalent fraction with a denominator of 120then write the original fractions in order from samllest to largest

Julius sold five times as many computers as sam sold last year. in total, they sold 78 computers. how many computers did julius sell?

Frank owns a $141,000 home, for which he has a 30-year mortgage in the amount of $700 a month. once he has paid off mortgage, how much will he have paid in investment? a. $111,000 b. $109,000 c. $120,000 d. $141,000