Answer:
1. (3^3 + 3^2)^2 actually equals (27 + 9)^2
which is the first mistake
2. (27 + 9)^2 does not equal (3^5)2, so (36)^2 does not equal 3^7
3. 3^7 DOES NOT EQUAL 21
Explanation:
when you add powered numbers together, it does not multiply it, as your example:
1. (3^3 + 3^2)^2 actually equals (27 + 9)^2
which is the first mistake
2. (27 + 9)^2 does not equal (3^5)2, so (36)^2 does not equal 3^7
3. 3^7 DOES NOT EQUAL 21