In order to keep up the same level of achievement, the ratio of "number of successfully completed questions" to "the number of attempted questions" should remain same.
more problems to complete = 45
let number of problems he need to successfully complete = x
[tex] \frac{12}{15}= \frac{x}{45} \\ \\x= \frac{12}{15} \times 45\\ \\ x=12 \times 3=36 [/tex]
He should complete 36 questions out of 45 successfully.
