1) Simplify
You combine the like terms.
a) 7y + 3y + 8
The like terms here are 7y and 3y. So add 7+3 and you get 10:
10y + 8
b) 7x+3y-2x-10y
The like terms here are 7x + -2x, and 3y + -10y. Add them and you'll get:
5x - 7y
c) 3x^2 + 7x - 9x
The like terms here are 7x and -9x. 3x^2 has an exponent so it's not included. So add the like terms and you get:
3x^2 - 2x
2) Solve
Here you need to isolate the variables.
a) 4x + 1 = 29
The first step is to subtract 1 on both sides.
4x = 28
Then divide both sides by 4.
x = 7
b) 7y - 11 = 2y + 29
Add 11 on both sides.
7y = 2y + 40
Then subtract 2y.
5y = 40
Finally, divide both sides by 5.
y = 8