42=7a+4(3a+1)

Solution for 42=7a+4(3a+1) equation:

Simplifying
42 = 7a + 4(3a + 1)

Reorder the terms:
42 = 7a + 4(1 + 3a)
42 = 7a + (1 * 4 + 3a * 4)
42 = 7a + (4 + 12a)

Reorder the terms:
42 = 4 + 7a + 12a

Combine like terms: 7a + 12a = 19a
42 = 4 + 19a

Solving
42 = 4 + 19a

Solving for variable 'a'.

Move all terms containing a to the left, all other terms to the right.

Add '-19a' to each side of the equation.
42 + -19a = 4 + 19a + -19a

Combine like terms: 19a + -19a = 0
42 + -19a = 4 + 0
42 + -19a = 4

Add '-42' to each side of the equation.
42 + -42 + -19a = 4 + -42

Combine like terms: 42 + -42 = 0
0 + -19a = 4 + -42
-19a = 4 + -42

Combine like terms: 4 + -42 = -38
-19a = -38

Divide each side by '-19'.
a = 2

Simplifying
a = 2