21. 3a + 5b = -27
4a + 10b = -46
how to solve with substitution

a = -4 and b = -3

Step-by-step explanation:

Step 1: Solve 3a + 5b = -27 for a

3a + 5b = -27

3a + 5b + -5b = -27 + -5b

(Add -5b go both sides)

3a = -5b- 27

3a = -5b - 27

3 3

(Divide both sides by 3)

a = -5 b - 9

3

Step 2: Substitute -5 b - 9 for a in 4a + 10b = -46

3

4a + 10b = -46

4(-5 b - 9) + 10b = -46

3

10 b - 36 = -46

3

(Simplify both sodes of the equation)

10 b - 36 + 36 = -46 + 36

3

(Add 36 to both sides)

10 b = -10

3

10/3 b = -10

10/310/3

(Divide both sides by 10/3)

b = -3

Step 3: Substitute -3 for b in a = -5/3 b - 9

a = -5/3 (-3) - 9

a = -4

(Simplify both sides of the equation)

no

step-by-step explanation: