Writing Equations 2

Sam owns three times as many marbles as Jenny. $S=3J$

Ed owns half as many marbles as Jenny. $2E=J$ or $E=0.5J$

How many marbles do they own together? $S+J+E=M$

Substituting so $J$ is the only variable results in $3J+J+0.5J=M$

This equation could be simplified to $4.5J=M$ . Without more information, it is impossible to know the total number of marbles any person has, but we can figure out the relative proportions.

"Sam ( $S$ ) owns three times as many marbles as Jenny ( $J$ )." $\rightarrow S = 3J$

"Ed ( $E$ ) owns half as many marbles as Jenny." $\rightarrow E = 0.5J$

"How many marbles ( $M$ ) do they own together?" $\rightarrow S + J + E = M \rightarrow \boxed{3J + J + 0.5J = M}$

Therefore, the answer is $3J + J + 0.5J = M$ .