Answer: Hello there!
in East middle school there are 58 left-handed students and 609 right-handed students.
You could calculate the ratio between them in the next way:
divide the biggest number by the smaller one:
x = 609/58 = 10.5.
then the proportion is 1:10.5 wich means that for every left-handed student, you have 10.5 right-handed students, but the 10.5 looks weird, we could write this ratio as 2:21 by multiplying each side by 2.
and now for every two lefthanded students, there are 21 right-handed students:
now you know that at West Junior High the proportion between left-handed students and right-handed students is proportional to the numbers at East Middle School.
this means that the ratios are equivalent, or:
if there are Y left-handed students at West Junior High, then there are X = 10.5*Y right-handed students in West Junior High.
Where X and Y are not necessarily equal than in East Middle School, just the ratios are proportional between them