Rahul's father's age is 3 times Rahul's age. After 15 years sum of their age is 90

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

If angle b measures 25°, what is the approximate perimeter of the triangle below? 10.3 units 11.8 units 22.1 units 25.2 units

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?