Fiscal multiplier math question

CFA Level I Economics
#1

From Kaplan:

Here, with a tax rate of 25% and an MPC of 80%, the fiscal multiplier is 1 / [1 – 0.8(1 – 0.25)] = 2.5, and the increase of $100 in government spending has the potential to increase aggregate demand by $250.

The answer that I calculate from the fiscal multiplier equation is 6.66.

Where is my math erroring?

#2
\frac{1}{1 - 0.8\left(1 - 0.25\right)} = \frac{1}{1 - 0.8\left(0.75\right)} = \frac{1}{1 - 0.6} = \frac{1}{0.4} = 2.5
#3

Those dasterdly parentheses.

Thank you!

#4

My pleasure.