Value of the digits in the hundreds place is how many times as much as the value of the digit in the tens place

In general, the place value of the hundreds place is 10x's greater than the value in the tens place.  It takes 10 tens to get you into the hunderds place.

That said, for specific numbers, like 421, the hundreds digit's value is 400 and the tens digit's value is 20, so the 4 in the hundreds is 20 times greater than the 2 in the tens.

But I think you're really asking about what I said in the first paragraph.

36 girls

step-by-step explanation:

the 48 boys is 4 parts of the ratio

divide 48 by 4 to obtain one part of the ratio

= 12 ← 1 part of the ratio

3 parts = 3 × 12 = 36 ← number of girls