42=3*5+b

Solution for 42=3*5+b equation:

Simplifying
42 = 3 * 5 + b

Multiply 3 * 5
42 = 15 + b

Solving
42 = 15 + b

Solving for variable 'b'.

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

Add '-1b' to each side of the equation.
42 + -1b = 15 + b + -1b

Combine like terms: b + -1b = 0
42 + -1b = 15 + 0
42 + -1b = 15

Add '-42' to each side of the equation.
42 + -42 + -1b = 15 + -42

Combine like terms: 42 + -42 = 0
0 + -1b = 15 + -42
-1b = 15 + -42

Combine like terms: 15 + -42 = -27
-1b = -27

Divide each side by '-1'.
b = 27

Simplifying
b = 27