Let x = 3y + 4z + 2. what happens to the value of x if the value of y is increased by 4 and the value of z is decreased by 2?

Subsitute y with y+4

subsitute z with z-2

xold=origianal value of x

xnew=new value of x

so

xold=3y+4z+2

xold=3y+4z+2

xnew=3 (y+4) + 4 (z-2) + 2

xnew=3y+12+4z-8+2

xnew=12-8+3y+4z+2

xnew=4+3y+4z+2

xnew=4 + (3y+4z+2)

xnew=4 + (xold)

so the value of xold increased by 4

x increased by 4