Ratio expresses the degree of proportionality between two or more numbers. It expresses the number of times one number is contained in another number.
In order to make the ratios equal, the relationship that exists between 9 and 36 has to be determined. 36 is a multiple of 9. It is 9 multiplied by 4. So, in order to make the ratios equal, multiply, 25 by 4.