Answer:
0.75 or three-fourth of a cup of nuts.
Step-by-step explanation:
Given that:
Original recipe has
1. One and half cups of peanut butter
2. Unknown number of cups of nuts, let this amount be
cups.
3. Three very ripe bananas.
Total amount of chips and nuts after doubling =
cups
Before doubling, total amount of chips and nuts = 
Now, as per given question statement:

Subtracting the number 1.5 from both the sides to find the value of
:

Therefore, <em>0.75 or three-fourth of a cup of nuts</em> is the original amount in the recipe.