Does anyone know how to do this by solving with substitution

Step-by-step explanation:

Question 1

System of equations is,

y = -6x (1)

y = -4x - 2 (2)

Substitute the value of y from equation (1) to equation (2)

-6x = -4x - 2

-6x + 4x = -2

-2x = -2

x = 1

From equation (1)

y = -6(1)

y = -6

Question (2)

System of equations is,

-y = x (1)

3x + 5y = 20 (2)

Substitute the value of x from equation (1) to equation (2)

3(-y) + 5y = 20

-3y + 5y = 20

2y = 20

y = 10

From equation (1)

-y = x

x = -10

Question (3)

System of the equations is,

y = -2x - 7 (1)

9x - 10y = 12 (2)

Substitute the value of y from equation (1) to equation (2)

9x - 10(-2x - 7) = 12

9x + 20x + 70 = 12

29x = 12 - 70

29x = -58

x = -2

From equation (1)

y = -2(-2) - 7

y = 4 - 7

y = -3

answer is the third choice:

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

step-by-step explanation: