Answer: First, you identify how many rises and runs the line is from each point on a graph (intersection). Then you take the y's and the x's and do y2-y1/x2-x1 to get the slope!
Swapping rows alters the sign of the determinant:

Multiplying a single row by a scalar scales the determinant by the same amount:

Then

Answer:
The total number of possibilities are 60.
Step-by-step explanation:
Given:
There are 6 digits and 3,7,9 are odd ones.
To Find:
How many possibilities are there for the rock's age
Solution:
Here condition is that number should start with odd digit
so there 3 number only as odd(3,7,9)
So it leaves 3 repeating numbers i.e.2
So permutation of 5 numbers with 3 odd numbers
So possible arrangement will be
nPr
n=5 ,r=3
So 5P3=5!/3!
And finally for all possibilities as
=3*(5!/3!)
=3*(20)
=60