Find the distance from point a(−1, 7) to the line y= 3x. round your answer to the nearest tenth.

The line joining A to y = 3x will be perpendicular to the latter so its slope will be -1/3.

its equation will be y - 7  = -1/3(x  + 1)

= y = -1/3x + 20/3

where the lines intersect:-

3x = -1/3x + 20/3
10/3 x  = 20/3

x =  2   and y =   3*2 = 6

so we need to find distance between (-1,7) and (2,6)  

this is  sqrt[((7-6)^2 + (-1-2)^2)]  =  sqrt 10   =  3.2 to nearest tenth.