Incorrect, he subtracted 10 (the amount spent) from 100 while he has to subtract the remaining amount to find the amount he spent meaning he has to subtract 90 from 100, not 10. The denominator is also wrong. The denominator would be 100, the original amount from which he wants to find the percentage. that would be
Since we know that there are exactly 180 degrees in any triangle, and if each angle is equal to 45 degrees, we must add 45 to 45 and then subtract the result from 180 to find the 3rd angle. Since 45+45=90,we subtract 180-90 and get 90 degrees or a right angle.
