Answer:
Equation:

Solve for n: n = 112
Explanation:
To first set up the equation, you need to look at the verbal description and translate into numbers and operations:
'three fourths a number' =

'plus 8' = + 8
'is' =
'20 less' = - 20
'the number' = n
Put the expressions together:
'three fourths a number plus 8':

'20 less than the number': n - 20
Set them equal to each other and solve:

Add 20 to both sides:

Subtract
from both sides:

Multiply both sides by
:

Solve for n: n = 112