Total no. of students = 1000

Ratio of boys to girls = 3 : 2

⇒ No. of boys = $(\frac{3}{5}\; \times \;1000 = 600)$

⇒ No. of girls = 1000 - 600 = 400

It is known that 88% of the boys passed

⇒ No. of boys passed = $(\frac{{88}}{{100}}\;\times\;600=528)$

⇒ No. of boys failed = Total no. of boys – No. of boys passed = 600 – 528 = 72

Similarly, it is known that 93% of the girls passed

⇒ No. of girls passed = $(\frac{{93}}{{100}}\; \times \;400 = 372)$

⇒ No. of girls failed = Total no. of girls – No. of girls passed = 400 – 372 = 28

So, Total No. of students failed = No. of boys failed + No. of girls failed