91Ó°ÊÓ

For each given value of \(x,\) determine the value of y that gives a solution to the given linear equations in two unknowns. $$x-4 y=2 ; \quad x=3, x=-0.4$$

Solve each system of equations by sketching the graphs. Use the slope and the \(y\) -intercept or both intercepts. Estimate each result to the nearest 0,1 if necessary. $$\begin{aligned} &s-4 t=8\\\ &2 s=t+4 \end{aligned}$$

Solve the given systems of equations by the method of elimination by substitution. $$\begin{aligned} &2 x+3 y=7\\\ &6 x-y=1 \end{aligned}$$

Evaluate the given determinants. $$\left|\begin{array}{cc} -20 & 110 \\ -70 & -80 \end{array}\right|$$

Evaluate the given third-order determinants. $$\left|\begin{array}{rrr} 20 & 0 & -15 \\ -4 & 30 & 1 \\ 6 & -1 & 40 \end{array}\right|$$

Find the slope of the line that passes through the given points. $$(-2.8,3.4),(1.2,4.2)$$

Solve the given systems of equations by the method of elimination by substitution. $$\begin{aligned} &6 s+6 t=3\\\ &4 s-2 t=17 \end{aligned}$$

Solve the given systems of equations. $$\begin{aligned}&18 x+24 y+4 z=46\\\&63 x+6 y-15 z=-75\\\&-90 x+30 y-20 z=-55 \end{aligned}$$

Evaluate the given determinants. $$\left|\begin{array}{cc} -6.5 & 12.2 \\ -15.5 & 34.6 \end{array}\right|$$

For each given value of \(x,\) determine the value of y that gives a solution to the given linear equations in two unknowns. $$3 x-2 y=9 ; \quad x=\frac{2}{3}, x=-3$$