1. 3x=18; you divide each side by 3 because you want to get the x by itself. When you do that, you get x=6.
2. Y+4=11; you subtract each side by 4 because you want to get the y by itself so you do the opposite of that is in front of the +4 (-4). When you do that, you get y=7.
3. W/5=6; you multiply each side by 5 because to get rid of the 5, you multiply(or do the opposite(inverse)) to get the w by itself. That would leave you with w=30.
4. 135=p+21; you subtract each side by 21 to get 114=p.
5. 2m-3=13; the easiest thing to do is to add 3 to both sides to get 2m=16. After that divide both sides by 2 to get m=8.
6. 3/4+a=2 1/4; if it's easier, turn the fractions into a decimal. Subtract both sides by 3/4 to get 1 1/2. a=1 1/2