Answer:
b=21
Explanation:
Since this a right triangle we can use the Pythagorean theorem
a^2 +b^2 = c^2
where a and b are the legs and c is the hypotenuse
20^2 +b^2 = 29^2
400 +b^2 = 841
Subtract 400 from each side
400-400 +b^2 = 841-400
b^2 = 441
Take the square root of each side
sqrt(b^2) = sqrt(441)
b =21