Word Problem Please Need help to solve this

Question

A university subject has three items of assessment – a quiz, an assignment and an exam. Suppose a student scored 4.5/10 on the quiz worth 25% and 72/90 on the assignment worth 35%. The remaining 40% weighting is for the exam. If this student would like to achieve a distinction (or 75%) mark overall in their subject, what mark do they require on their exam?

Answer 1

4.5/10 = a grade of 45%

72/90 = 8/10 = a grade of 80%

45(.25) + 80(.35) + x(.40) = 75

11.25 + 28 + .4x = 75

.4x = 75-11.25-28 = 75-39.25 = 35.75

x = 35.75/.4 = 89.375 on the final exam to get a weighted average of 75