Find the distance between points a(2,4) and b(-4,-3 round answer to nearest tenth
7.2
12.2
11.2
9.2

For this, you'd need to know the Euclidean Distance Formula (it's basically the most common one)
                  −−−−−−−−−−−−−−−−
distance=√(x2−x1)^2+(y2−y1)^2

You would just plug in the points so A is at (2,4) this means that 2 is x1 and 4 is y1. Same with point B but instead of -4 being x1 it would be x2 alsong with -3 being y2.

Ok so when you plug in the points, you get this equation that should be simplified

                  −−−−−−−−−−−−−−−−
distance=√(-4−2)^2+(-3−4)^2

                  −−−−−−−−−−−−−−−−
distance=√(-4+(-2))^2+(-3+(-4))^2

I negated the 2 and 4 because of the rules with negatives which basically states that if a positive number is being subtracted from a negative number, it will be multiplied by -1 to make the positive a negative number. Also the subtraction sign will be changed into an addition sign. 
Simplify this. 

                  −−−−−−−−−−−−−−−−
distance=√(-6)^2+(-7)^2

6^2 = 36
7^2= 49

                  −−−−−
distance=√36+49

36+49=85
                  −−
distance=√85

Then the square root of 85 is 9.21954445729, but because we are rounding to the nearest tenth the distance is 9.2.