Question 408723
After lunch, she has eaten {{{(7/12)*(5/12) = 35/144}}}.
Hence all in all she has eaten {{{5/12 + 35/144 = 95/144}}} of her orange.

Well, think about it:
Before lunch she ate 5/12 of the orange, which leaves 7/12 of the orange BEFORE lunch.

AFTER lunch, she ate 5/12 of the remaining 7/12, and that is {{{(5/12)*(7/12) = 35/144}}}.  That is the portion eaten AFTER lunch.  So the portion eaten BEFORE lunch, PLUS the portion eaten AFTER lunch must be {{{5/12 + 35/144 = 95/144}}} of the orange.