Answer:
150
Step-by-step explanation:
Sum the parts of the ratio, 1 + 3 + 6 = 10 parts
Divide the number of marbles by 10 to find the value of one part of the ratio.
250 ÷ 10 = 25 ← value of 1 part of the ratio, thus
number of blue marbles = 6 × 25 = 150
