If chase won the next 18 matches then he will be able to get a 75% winning record.
Explanation:
Let the no. of games chase has to win be 'y'.
He has won 18 matches out of 30.
If he won y matches more he will have a 75% winning record.
To find the percentage we should calculate,
% = (no. Of matches won) x 100/ (total no. of matches)
As the no. of matches won increases, the total no. of matches also increases.
So y should be added to the matches won and also to the total no. of matches played.
[(18+y) /(30+y) ] x 100 = 75%
[(18+y) (100) ] = 75(30+y)
1800 + 100y = 2250 + 75y
100y - 75y = 2250 - 1800
25y = 450
y = 18
So if chase won next 18 matches then he will be able to get a 75% winning record