Question

100 points in correct answer deduction 40 in every wrong. 20 questions asnwered and the score 180 points how many wrong answer did he get?

Answer 1

13 incorrect answers

Answer 2

Let the right = x

Let the wrong = y

100x - 40y = 180 (1)

x + y = 20 (2) Rearrange (2) to prepare for a substitution

x = 20 - y (3)

100(20 - y) - 40y = 180 Put (3) into (1) Remove the brackets.

2000 - 100y - 40y = 180 Collect like terms

2000 - 140y = 180 Subtract 2000 from both sides

-140y = 180 - 2000

-140y = -1820 Divide by - 140

y = -1820/-140

y = 13

Answer: He had 13 incorrect answers