The sum of two y and three is the same as the difference of three y and one

The sum of two y and three
2y + 3

the difference of three y and one
3y - 1

is the same as means equal to. Set 2y + 3 equal to 3y - 1 for our final algebraic expression:
2y + 3 = 3y - 1

If the problem asks you to solve for y, subtract 2y from each side:
3 = y - 1

Add 1 to each side:
y = 4