3/7 of the students in a class play a sport, and of these students, 1/3 play soccer. what fraction of the class plays soccer?
a) 1/7
b) 4/21
c) 4/10
d)4/7
?

Marks scored by Rex in his three tests are 84 ,86 and 92. Let marks scored by Rex in his fourth test be x.

Average of the marks =

Given average of all four marks is 90.

Forming an equation.

Solving for x.

Cross multiplying we have:

262+x=360

Subtracting both sides by 262

x=360-262

x= 98.

Answer :Rex must score 98 marks in his fourth test to have an average of 90 % .