Answer: x=4, y=1
Step-by-step explanation:
1) Factor out the common term 7.
42 =7(x - 1 + 3y)
2) Divide both sides by 7.
42/7=x-1+3y
3) Simplify to 6.
6 = x - 1 + 3y
4) Add 1 to both sides.
6+1=x+3y
5) Simplify 6+1 to 7.
7=x+3y
6) Subtract 3y from both sides.
7−3y=x
7) Switch sides.
x=7−3y
8) Plug x=7−3y into original equation
7(7-3y) -7 + 21y
9) Expand by distributing terms.
49−21y−7+21y
10) Collect like terms.
(49−7)+(−21y+21y)
11) Simplify.
42
12) Take the original equation 42=7x -7 + 21y
knowing (−21y+21y) cancels each other out means y=1
13) Simplify 21y when y=1
42=7x -7 + 21
14) Subtract 21 from both sides.
42-21=7x-7
15) Simplify.
21=7x-7
16) Add 7 to both sides
21+7=7x
17) Simplify.
28=7x
18) Divide each side by 7
x=4
