AThere is a stack of sweaters at the store. Six sweaters have 5 buttons each. One sweeter has 4 buttons. How many buttons do the sweaters have altogether?

34 buttons

Explanation:

6 x 5 = 30

1 x 4 = 4

30 + 4 = 34

substitute y = 2x - 4 to x + 2y = 12:

x + 2(2x - 4) = 12     use distributive property

x + (2)(2x) + () = 12

x + 4x - 8 = 12     add 8 to both sides

5x = 20     divide both sides by 5

x = 4

put the value of x to the first equation:

y = 2(4) - 4

y = 8 - 4

y = 4