Question

the ratio of red marbles to blue marbles in a bag is 4:7. There are 16 red marbles.How many blue marbles are there? solve for indicated variable.

Answer 1

4x - number of red marbles
7x - number of blue marbles


`4x=16\\ x=4\\\\ 7x=7\cdot4=\boxed{28} \leftarrow \hbox{number of blue marbles}`

Answer 2

red marbles : blue marbles = 4:7

16 - red marbles
x - blue marbles


`(16)/(x)=(4)/(7) \\ 16 * 7 = 4x \\ 4 * 7 = x \\ x=28`

There are 28 blue marbles.