p+[0.5p+3]=21

Solution for p+[0.5p+3]=21 equation:

Simplifying
p + [0.5p + 3] = 21

Reorder the terms:
p + [3 + 0.5p] = 21

Remove brackets around [3 + 0.5p]
p + 3 + 0.5p = 21

Reorder the terms:
3 + p + 0.5p = 21

Combine like terms: p + 0.5p = 1.5p
3 + 1.5p = 21

Solving
3 + 1.5p = 21

Solving for variable 'p'.

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

Add '-3' to each side of the equation.
3 + -3 + 1.5p = 21 + -3

Combine like terms: 3 + -3 = 0
0 + 1.5p = 21 + -3
1.5p = 21 + -3

Combine like terms: 21 + -3 = 18
1.5p = 18

Divide each side by '1.5'.
p = 12

Simplifying
p = 12