Originally Posted by
HallsofIvy What help do you want? You cite Cramer's rule. Do you know what that is?
Cramer's rule says that the solutions of a system of equations
$\displaystyle a_{11}x+ a_{12}y+ a_{13}z= b_1$
$\displaystyle a_{21}x+ a_{22}y+ a_{23}z= b_2$
$\displaystyle a_{31}x+ a_{32}y+ a_{33}z= b_3$
are given by
$\displaystyle x=\frac{\left|\begin{array}{ccc}b_1 & a_{12} & a_{13} \\ b_2 & a_{22} & a_{23} \\ b_3 & a_{32} & a_{33}\end{array}\right|}{\left|\begin{array}{ccc} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33}\end{array}\right|}$
$\displaystyle y=\frac{\left|\begin{array}{ccc}a_{11} & b_2 & a_{13}\\ a_{21} & b_2 & a_{23}\\ a_{31} & b_3 & a_{33}\end{array}\right|}{\left|\begin{array}{ccc} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33}\end{array}\right|}$
$\displaystyle z=\frac{\left|\begin{array}{ccc}a_{11} & a_{12} & b_1 \\ a_{21} & a_{22} & b_2 \\ a_{31} & a_{32} & b_3\end{array}\right|}{\left|\begin{array}{ccc}a_{ 11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33}\end{array}\right|}$
Put in the numbers for your equations and calculate the determinants. Have you done that yet?