Use Subtraction
1. Subtract
x+2y=7
3x-2y=-3
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4x+0y=4 SIMPLIFY 4x=4
2. DIVIDE
4x=4
x=1
Substitute that into either of the original equations to get x=1, y=3
Answer: Choice C.
and Choice E. 
Step-by-step explanation:
Algebraic exponents.
It would be be because they didn’t distribute the 8n to the 20
Answer:
80
Step-by-step explanation:
28-28=0
0-12= -12
28+12 = 40
28-40 = -12
40 is the increase
40 is half of 80
So, the answer is 80
To check: -12 + 40 (half of a number; 80) = 28
Hope this makes sense. If you require further information, do not hesitate to ask!