The difference of 12 and a number x . write as an expression

uh hello. i know i'm stupid and stuff but is suck at math so yea. for answers btw

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).

Which value would be a solution for x in the inequality 47-4x< 7

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827