Answer:
18 marbles
Explanation:
Step 1
Express the fraction of each type of marble as a function of the total number of marbles as shown;
Let;
total marbles=x
red marbles=3/(3+4)=3/7x
blue marbles=4/7 x
But x=42 marbles
The total number of marbles for each type can be expressed as;
total number of red marbles=fraction of red marbles×total number of marbles
where;
fraction of red marbles=3/7 x
total number of marbles=42
replacing;
total number of red marbles=(3/7)×42=18 marbles
total number of blue marbles=fraction of blue marbles×total number of marbles
where;
fraction of blue marbles=4/7 x
total number of marbles=42
replacing;
total number of blue marbles=(4/7)×42=24 marbles