Answer:
30 blueberries
Explanation:
the ratio 1:7 is just like the fraction 1/7
the ratio of 1:7 must be the same as the ratio of x:210 with x being blueberries
1/7 = x/210 is a way to solve this equation
to solve this we can divide multiply the top and bottom of 1/7 by 30
1/7 * 30/30 = 30/210
this is your answer
30 blueberries