Answer:

Step-by-step explanation:
In this problem we are calculating the relative frequency conditional by columns.
Therefore the sum of the frequencies of each column must be equal to 1.
Then we use this condition to calculate the values of a and b
So:


Finally

Cross multiply and you get
50t = 40 x 16
50t = 640
t = 640/50
t = 12.8
Answer:
I think 3 or 4 I don't know which one
83-73 will make up to 155