To solve this equation, isolate the variable for which you are solving (a) on one side of the equation and put everything else on the other side.

a + 3x = 8a + x + 2
a = 8a + x + 2 - 3x
a - 8a = x + 2 - 3x
-7a = -2x + 2
a = \( \frac{-2x + 2}{-7} \)
a = \( \frac{-2x}{-7} \) + \( \frac{2}{-7} \)
a = \(\frac{2}{7}\)x - \(\frac{2}{7}\)

You need to find the value of a so solve the first equation in terms of x:

7a + x = 6
x = 6 - 7a

then substitute the result (6 - 7a) into the second equation:

-9a - 3(6 - 7a) = 5
-9a + (-3 x 6) + (-3 x -7a) = 5
-9a - 18 + 21a = 5
-9a + 21a = 5 + 18
12a = 23
a = \( \frac{23}{12} \)
a = 1\(\frac{11}{12}\)

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

6a + 9a = 15a

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(7a)(3ab) - (5a²)(3b)
(7 x 3)(a x a x b) - (5 x 3)(a² x b)
(21)(a¹⁺¹ x b) - (15)(a²b)
21a²b - 15a²b
6a²b

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).