Answer:
Side 1: 5
Side 2: 4
Side 3:

Perimeter:

Explanation:
For side 1 and side 2, notice that it fits the grid spaces perfectly. For side 1, you can count 5 spaces. For side 2, you can count 4 spaces. For side 3, notice that the grid spaces aren't even. Some of them are cut through. We can use the Pythagorean Theorem.
Pythagorean Theorem:
, there a and b are legs and c is hypotenuse.
[simplify]
[add]
[square root both sides]

Perimeter is finding the sum of all the sides together.
[simplify]
