We know that a = b and c = 30
Since b + 30 = 90, we know b = 60.
That means a = 60
a = 60
b = 60
c = 30
78 cups of coffee (stem 7 and leaf 8)
Probability = 1/4, or 25%
The probability of rolling an even number on a die: 1/2
(1, 2, 3, 4, 5, 6; 3 are even numbers, 3/6 = 1/2)
The probability of flipping heads: 1/2
(heads or tails)
1/2 x 1/2 = 1/4