First, we need to simplify the equation given:

3.2 - 5a = -1.8

Add 5a to both sides:

3.2 = -1.8 + 5a

Subtract -1.8 from both sides:

3.2 + 1.8 = 5a

5 = 5a

Now, solve for a by dividing both sides by 5:

5/5 = a

a = 1

Next, we need to find the value of 4a:

4a = 4(1) = 4

Therefore, 4a = 4.