Starting with the given 20.5=15.5+(-3.6x)+1.8x, rewrite "+(-3.6x)" as "-3.6x:"
20.5=15.5-3.6x+1.8x
Next, combine like terms: 20.5-15.5 = -3.6x+1.8x, or
5 = -1.8x
Dividing both sides by -1.8 yields -2.78 = x, or x = -7/9
Please ensure that you have copied this problem down correctly.
