?$解:假設(shè)甲、乙兩種商品的進(jìn)貨單價(jià)各為\ x, y\ 元.\ $? ?$根據(jù)題意,得\ \left\{\begin{array}{l}x+y=5, \\ 3(x+1)+2(2 y-1)=19 .\end{array}\right.\ 解得\ \left\{\begin{array}{l}x=2, \\ y=3 .\end{array} \right.\ $? ?$ $? ?$解:設(shè)計(jì)劃生產(chǎn)零件\ x\ 個(gè)，預(yù)定期限\ y\ 個(gè)，$? ?$則\ \left\{\begin{array}{l}2 y=x-100 \\ 25 y=x+50\end{array}\right. , 解得\ \left\{\begin{array}{l}x=700 \\ y=30\end{array}\right.\ $? ?$ $? ?$解:設(shè)有\(zhòng) x 人捐 2 元, 有\(zhòng) y\ 人捐 5 元.\ $? ?$根據(jù)題意, 得\ \left\{\begin{array}{l}x+y+6+7=55, \\ 2 x+5 y+6 \times 1+10 \times 7=274 .\end{array}\right.\ 解得\ \left\{\begin{array}{l}x=4, \\ y=38 .\end{array}\right. .\ $? ?$ $? ?$解：設(shè)面值為 2 元的人民幣有\(zhòng) x\ 張, 面值為 1 元的人民幣有\(zhòng) y\ 張,\ $? ?$面值為 5 角的人民幣有\(zhòng) z\ 張，$? ?$根據(jù)題意可得\ \left\{\begin{array}{c}x+y+z=24 \\ 2 x+1 y+0.5 z=29 \text {, 可得 } \\ x+6=y\end{array}\right.\ \ \left\{\begin{array}{l}x=7 \\ y=13 \\ z=4\end{array}\right.\ $?
?$ $? ?$解:設(shè)可制作甲種小盒\(zhòng) x\ 個(gè),乙種小盒\(zhòng) y\ 個(gè).$? ?$根據(jù)題意, 得\ \left\{\begin{array}{l}x+2 y=150, \\ 4 x+3 y=300,\end{array}\right.\ 解得\ \left\{\begin{array}{l}x=30, \\ y=60 .\end{array}\right.\ $? ?$故可制作甲種小盒 30 個(gè), 乙種小盒 60 個(gè).$?
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