Can someone understand this i know its substitution for sure if i dont get wrong

4x - y = 3

y = 2x + 13

Substitute the second equation into the first equation:

4x - y = 3  [since y = 2x + 13, you can substitute (2x + 13) for "y" in the equation]

4x - (2x + 13) = 3    Distribute/multiply - into (2x + 13)

4x - 2x - 13 = 3  

2x - 13 = 3       Add 13 on both sides

2x = 16     Divide 2 on both sides

x = 8

Now that you know x = 8, plug it into one of the equations to find y

y = 2x + 13

y = 2(8) + 13

y = 16 + 13

y = 29

x = 8, y = 29  or  (8, 29)

[proof]

4x - y = 3

4(8) - 29 = 3

32 - 29 = 3

3 = 3

y = 2x + 13

29 = 2(8) + 13

29 = 16 + 13

29 = 29

answer is the third choice:

3x^5+4x^4+x^3+2x^2-10x-7=0

step-by-step explanation: