Find the measure of angle k

What is the range of the data below? .8090100

Find the gradient of f(x,y,z)equals=left parenthesis x squared plus y squared plus z squared right parenthesis superscript negative 1 divided by 2 baseline plus ln left parenthesis x right parenthesis x2+y2+z2−1/2+ln(xyz) at the point left parenthesis negative 2 comma 1 comma negative 2 right parenthesis(−2,1,−2).

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles