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