Count numbers in a list if a condition is true

I am trying to count how often number values occur in a list, with the caveat being if and only if another corresponding value is a certain number

For instance, let's say I want something to count the frequency of "2" in a range of cells from A1:A100.

However, it only counts this 2 when the corresponding cell B1:B100 has a value of 6. If the B column cell is any number other than 2, it does not count.

I tried using Excel's help, but could not get the formula to work using a count statement, or a sum/if combination statement

Here's what I tried that did not work

=SUM(IF(A1:A100="2",IF(B1:B100="9",1,0)))