How do you solve d=7a d=4a+30

a = 10, d = 70

Step-by-step explanation:

Solve the following system:

{d = 7 a | (equation 1)

{d = 4 a + 30 | (equation 2)

Express the system in standard form:

{ - (7 a) + d = 0 | (equation 1)

{ - (4 a) + d = 30 | (equation 2)

Subtract 4/7 * (equation 1) from equation 2:

{ - (7 a) + d = 0 | (equation 1)

{0 a + (3 d) / 7 = 30 | (equation 2)

Multiply equation 2 by 7/3:

{ - (7 a) + d = 0 | (equation 1)

{0 a+d = 70 | (equation 2)

Subtract equation 2 from equation 1:

{ - (7 a) + 0 d = - 70 | (equation 1)

{0 a+d = 70 | (equation 2)

Divide equation 1 by - 7:

{a+0 d = 10 | (equation 1)

{0 a+d = 70 | (equation 2)

Collect results:

Answer: {a = 10, d = 70