The two solutions presented above are wrong.
Apologies: I’m so use to seeing wrong answers, and the large drop in the x value (weight) are common for these types of questions;
I failed to check and verify my own work.
These types of questions require careful reading to understand what it is asking for.
Such questions are common in science and statistics, both in academics and in the real-world.
The mathematical solution seems paradoxical, but it’s not; it’s the language of the question that gives this illusion. Banana Paradox
\( {\text { Deleted Equation }}\)
\(\text { Here’s the correct equation. }\\ x=8+\dfrac{90}{100}x\\ x=80.0 \;Lbs\\ \text { The weight of the grapefruit is $80.0$ Lbs } \)
This now agrees with Badada’s and EP’s solutions above, and Dragan’s solution below.
Related question, with an expanded solution method.
https://web2.0calc.com/questions/help-asap-thanks_2#r5
GA