Answer:
2 : 5
Step-by-step explanation:
In order to obtain the ratio between numbers, we divide by the largest common factor between both.
In this question, the numbers are;
36 : 90
The largest common faction is 18. Dividing both numbers by 18, we have;
36 / 18 : 90 / 18
2 : 5
The ratio is; 2 : 5
