Answer: 26 feet.
Step-by-step explanation:he
The exercise is not written clearly. Assuming that it asks to find the amount of lumber (in feet) John needs for 3 shelves, let "x" represents that amount of lumber in feet.
Based on the data provided, you know that one shelf requires feet of lumber.
You can convert the Mixed number to Decimal number applying these steps:
1. You must divide the numerator of the fraction by the denominator.
2. You must add the result obtained to the Whole number part.
Then you get:
Knowing this, you can set up the following proportion:
Finally, you must solve for "x" in order to find its value. This is: