It takes $12$ hours to fill a swimming pool using two pipes. If the pipe of larger diameter is used for $4$ hours and the pipe of smaller diameter is used for $9$ hours, only half of the pool is filled. How long would each pipe take to fill the swimming pool?

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} 8x+5y=9 \\ 3x+2y=4 \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} 2x-3y=7 \\ 5x+y=9 \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} 2x+3y=8 \\ 2x=2+3y \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$\begin{array}{r}0.2x+0.1y=25\\ 2(x-2)-1.6y=116\end{array}$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} 6x=7y+7 \\ 7y-x=8 \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} y=4x-7 \\ 16x-5y=25 \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$$\begin{gathered} 2x+7y=39 \\ 3x+5y=31 \end{gathered}$$

Solve the following pairs of linear (simultaneous) equations using method of elimination by substitution:

$\begin{array}{r}1.5x+0.1y=6.2\\ 3x-0.4y=11.2\end{array}$