Hello!
To solve this, first perform the opposite operation for the last operation (on the left side) on both sides. The last operation of the left side is squaring. Therefore, square root both sides.
Please note that you must include ±. This is because the square root of 64 can be either positive or negative, as a square of either a positive or negative number is positive.
Now, add 9 to both sides.
There are 2 solutions from here. One comes from adding 8, and the other subtracting 8. Therefore, the two solutions are:
y = 9 + 8 = 17
y = 9 - 8 = 1
Therefore, your two solutions are 17 and 1.
Hope this helps!