Ok my last question . i don't understand how to get the lengths of the legs at all so

If the legs of a right triangle are lengths a and b and the hytponuse is legnth c then
a²+b²=c²

so if the hyptonuse is 20 then
a²+b²=20²
a²+b²=400
hmm, what combos can we do?
find the values of a and b such taht they are whole numbers and a²+b²=400

looking at all the squares from 1 to 20

1²=1
2²=4
3²=9
4²=16
5²=25
6²=36
7²=49
8²=64
9²=81
10²=100
11²=121
12²=144
13²=169
14²=196
15²=225
16²=256
17²=289
18²=324
19²=361
20²=400

which pairs add up to 400?
the only pair is 144+256 which is 12²+16²

the legs are length 12 units and 16 units