Question

good answer will be marked.​

Answer 1

$\huge{\boxed{\boxed{\mathfrak{\underline{\overline{\red{S{\green{o{\orange{l{\blue{u{\pink{t{\purple{i{\color{silver}o{\color{cyan}n}}}}}}}}}}}}}}}}}}}$

Let, Correct answers be x and Incorrect answers be y.

Total no. of questions include correct and incorrect answers.

∴ x + y = 100 _________(1)

For correct answer the student gets 5 marks and for incorrect answers -2 marks. The student gets 220 marks as total.

∴ 5 marks for correct answer - 2 marks for incorrect answers = 220

⇒5x - 2y = 220 ______(2)

(1) × 2 we get

2x + 2y = 200 _______(3)

(3) + (2)

$\: \: \: \: \: \: \: 2x + { \cancel{2y}} = 200$

$+ \: \: \: 5x - {{ \cancel{2y}}} = 220$

$\: \: \: \: \: \: \: { \overline{ \underline{ 7x + 0y = 420}}}$

$x = \frac{ \cancel{420} { \:}^{60} }{ \cancel7} \\ \boxed{ x = 60}$

So, the student attempted 60 answers correctly.