We need to use the Pythageorum Theorum formula which is .
So we already know the c and b which are 29 and 20 and we are trying to find b or a in the formula so.
We have to plug the numbers 29 and 20 into the formula and do the steps which is to sqaure them. So 29 and 20 squared are 841 and 400.
So we have to plug those numbers into the formula and it looks like this now . So now we have to get a squared alone and to do tha we subtract 400 from 841 which is 441. So now to find a we have to find the square root of a and 441 which is a and 21 so b is 21.