A postulate is an assumption we use for mathematical reasoning; it isn't yet proven. once it's proven, it becomes a theorem.
Answer:
let required no be x

by doing crisscrossed multiplication

42=7x
dividing both side by 7

6=x
therefore x=6
therefore value of remaining no.is 6
Neither one of the slopes are going to be minus. It means you are travelling backwards in time, which is wonderful if you are a sci-fi fan, but not so good if you are Sharon. A and D has Sharon going from 70 to 0. That can't be happening so both are wrong.
Now you have to decide between B and C. The intersection point has Sharon going upwards until she is 20. She started out at 70. The graph has John starting at 70. That's not right.
So we've eliminated A,D and now C.
The answer must be B. They meet when Sharon is 90 and John is about 22.5 which is what it should be.
X^2 * 5,x^4 so B is the answer
C. 20% because 15 goes into 75 5 times, and to find the percentage you would divide 100 by that number, 5, to get 20. So he has gone 20%