He might have used Charles? Or he has hacked before, and is experienced with hacking.
A) The answer is one solution, neither
6x + 2(2x - 3) = 24 + 9x
6x + 2 * 2x + 2 * (-3) = 24 + 9x
6x + 4x - 6 = 24 + 9x
10x - 6 = 24 + 9x
10x - 9x = 24 + 6
x = 30
b) The answer is infinity solutions, identity
<span>25 – 4x = 3(5 – x) + 10 – x
25 - 4x = 3 * 5 - 3 * x + 10 - x
25 - 4x = 15 - 3x + 10 - x
25 - 4x = 25 - 4x
4x - 4x = 25 - 25
0x = 0
x can be any number, so an infinite number of solution
c) The answer is no solution, contradiction
</span><span>4(x + 2) = 2x + 7 + 2(x – 10)
4 * x + 4 * 2 = 2x + 7 + 2 * x - 2 * 10
4x + 8 = 2x + 7 + 2x - 20
4x + 8 = 4x - 13
4x - 4x = - 8 - 13
0 = -13
this is contradiction</span>
202
-184
-------
18
Hope this helps! :)
x+5y=8... equ 1
-x+2y=-1 ..... equ2
Add equ 1 to equ 2
0x+7y=7
7y=7
Y=1
Subsitute the value of y in equ 1 or equ 2
By subsituting In equ 1
X+5(1)=8
X=3