Boys                Girls                     Total

Before         90                    48                        138

Left               u                      u                       138-2u

After         90-u                 48-u   

20% (=1/5) of remaining students are girls.

(1/5)(138-2u) = 48 – u     <——– x 5 on both sides

138 -2u = 240 – 5u

3u = 102

u = 34

Hence remaining students in the canteen = 138 – 2(34) = 70

PS: Please click ” Accept Answer” if the answer is correct.

Hi Prettyhomework,

This answer is correct, I only made a typo error in writing 90 as 98 earlier

Ooh… I’m starting to appreciate model drawings 🙂