Let \( x \) represent last year’s budget amount.
According to the information provided, the school plans to spend twice last year's amount, minus the cost of the disco ball. Therefore, we can express the equation as follows:
\[ 2x - 150 = 1500 \]
Now, filling in the blanks, we get:
- a = 2
- blank = x
- blank = 150
- blank = 1500
So the complete equation is:
\[ 2(x - 150) = 1500 \]