Question

Помогите решить пожалуйста

Answer 1

1

$\begin{equation*}\begin{cases}\frac{1}{5}a-\frac{1}{4}y=1 |\cdot 100\\20a-26y=25\\ \end{cases}\begin{cases}20a-25y=100\\20a-26y=25\\ \end{cases}\begin{cases}20a=25y+100\\20a-26y=25\\ \end{cases}\end{equation*}$

$\begin{equation*}\begin{cases}20a=25y+100|:5\\25y+100-26y=25\\ \end{cases}\begin{cases}4a=5y+20\\-y=25-100\\ \end{cases}\begin{cases}4a=5y+20\\y=75\\ \end{cases}\end{equation*}$

$\begin{equation*}\begin{cases}4a=5\cdot 75+20\\y=75\\ \end{cases}\begin{cases}4a=395 \\y=75\\ \end{cases}\begin{cases}a=\frac{395}{4} \\y=75\\ \end{cases}\begin{cases}a=98\frac{3}{4} \\y=75\\ \end{cases}\end{equation*}$

2

$\begin{equation*} \begin{cases}2x+10y=25|\cdot 2\\4x-5y=3\end{cases} \begin{cases}4x+20y=50\\4x-5y=3\end{cases}\begin{cases}4x=50-20y\\4x-5y=3 \end{cases}\end{equation*}$

$\begin{equation*} \begin{cases}4x=50-20y\\50-20y-5y=3 \end{cases} \begin{cases}x=12,5-5y\\25y=47 \end{cases} \begin{cases}x=12,5-5y\\y=\frac{47}{25} \end{cases}\end{equation*}$

$\begin{equation*}\begin{cases}x=12,5-5\cdot \frac{47}{25}\\y=\frac{47}{25} \end{cases}\begin{cases}x=12,5-9,4\\y=1\frac{22}{25} \end{cases}\begin{cases}x=3,1\\y=1\frac{22}{25} \end{cases}\end{equation*}$