Jon has a wingspan of 5'6'' and jim has a wing span of 6' what is the largest diameter of tree they wrap their arms around and still touch fingers

The answer is 43.95 in ≈ 44 in

Step 1. Sum up their wingspans which will reflect the perimeter of the tree they wrap.
Step 2. From the calculated perimeter in step 1, find the diameter.

Step 1.
Perimeter of the tree is the sum of their wingspans:
P = 5'6'' + 6' 
5'6'' = 5 * 12 in + 6 in = 66 in
6' = 6 * 12 in = 72 in
P = 66 in + 72 in = 138 in

Step 2.
Perimeter of a circle with radius r is:
P = 2 r π
Since diameter is twice of radius (d = 2r), then
P = d * π

P = 138 in
π = 3.14
138 in = d * 3.14
d = 138 in / 3.14
d = 43.95 in ≈ 44 in