You would multiply everything by 3 so it’s would be
2/3(3)x + 7(3) = 1/4(3)y
2x + 21 =3/4y
Then you would multiply everything by 4
2(4)x + 21(4) = 3/4(4)y
8x + 84 = 3y
Then you would subtract 84 from both sides
8x + 84 - 84 = 3y - 84
Because of the positive and negative 84 cancel out so it’s 0. It would look like this
8x = 3y - 84
Then subtract 3y from both sides
8x - 3y = -84
That would be your final answer.