the length of a rectangle is 5cm, and the width is 2 cm. If both the length and the width are increased by equal amounts, the area of the rectangle is increased by 60cm ^2 find the length and width of the larger rectangle

Her conclusion that 90% of the student body wants the colors changed is an INCORRECT conclusion. The 90% out of 100% is not referring to the total numbers of the student body.For example, 100 people are members of student body if only 50 members responded the survey, then we have:
 90% of 50 members who answered the survey said that they want the changed.