Question 166430
eliminate the same variable from two different PAIRS of equations, leaving two new equations with two unknowns


multiply 2nd eqn by -3 and add to 1st eqn __ -7y+10z=-21


multiply 3rd eqn by -3 and add to 2nd eqn __ 11y-9z=33


multiplying 1st new eqn by 11 __ -77y+110z=-231


multiplying 2n new eqn by 7 __ 77y-63z=231


adding eqns __ 47z=0 __ z=0


substituting __ 11y-9(0)=33 __ y=3


substituting __ x-3(3)+2(0)=-12 __ x-9=-12 __ x=-3