[tex]3y-5=4[/tex]
We add 5 to both sides of the equation and we get:
[tex]3y-5+5=4+5 \\ 3y=9[/tex]
We divide both sides by 3, to leave the variable y on the left-hand side
[tex] \frac{3y}{3} = \frac{9}{3} \\ y=3[/tex]
Therefore y is equal to 3.
What we have performed above is the addition property of equality which is whatever number you add to both sides of the equation would still hold, and the multiplication property of equality means that whatever number you multiply to both sides of the equation then the equation holds (we multiplied 1/3 in the solution above).