A ratio is a kind of fraction. So a:b is the same as a/b where a and b represent numbers. Example: let’s say there are 30 students in your grade. If the ratio of boys to girls is 2:3 it means that boys÷girls=2/3.
How many boys? To answer this draw a box to represent the 30 students in the grade. Now divide this box into 5 (2+3=5 boxes represent boy and girl students in total) equal boxes, so in each box there will be 6 students. Two boxes represent the boys and three boxes represent the girls. Two boxes=12 boys and three boxes=18 girls. 12÷18=2÷3=2/3=2:3.