lets write the problem info into an equation and solve step by step:
7(1/3 + 4/5)
the minimum common multiple of 3 and 5 is 15, so we multiply and divide the fractions by a proper number to convert them to be divided by 15 so is easier to add them:
(1/3)(5/5) = (1*5)/(3*5) = 5/15
(4/5)(3/3) = (4*3)/(5*3) = 12/15
so we substitute in the original equation:
7(1/3 + 4/5)
= 7(5/15 + 12/15)
= 7(17/15)
= (7*17)/15
= 119/15
