Solve the systems of equations.Using Kirchhoff's laws (see the chapter introduction; the equations can be found in most physics textbooks) with the electric circuit shown in Fig. $5.43,$ the following equations are found. Find the indicated currents (in $\mathrm{A}$ ) $I_{1}, I_{7}$, and $I_{3}$.$$\begin{aligned}
&1.0 I_{1}+3.0\left(I_{1}-I_{3}\right)=12\\
&\begin{array}{l}2.0 I_{2}+4.0\left(I_{2}+I_{3}\right)=12 \\1.0I_{1}-2.0 I_{2}+3.0 I_{3}=0\end{array}\end{aligned}$$
(FIGURE CANT COPY)