In order to divide a whole number by a decimal, here is what you have to do to make things easier:
since 0.36 has two digits after the comma, you just need to disregard the decimal and create the smallest whole number you can. Here, that would be 36 (you have multiplied 0.36 by the number of the digits, which is two: 0.36 * 100 = 36). However, you will also have to multiply 90 by 100 in order to make things even.
So, here is how to calculate this:
90 * 100 / 0.36 * 100 =
9000 / 36 =
250
The correct answer is 250.