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?

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

He had 13 incorrect answers

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sorry can't

step-by-step explanation:

i googled though and something came up but it was in science langueage not common english sooo