?$解:根據(jù)題意, 得\ \left\{\begin{array}{l}(b-a) \times 15 \times 30=22500, \\ {[(1-20 \%) b-a] \times(15+10) \times 30=22500 .}\end{array}\right.\ \ $? ?$解這個方程組, 得\ \left\{\begin{array}{l}a=50, \\ b=100 .\end{array}\right.\ $? ?$ $? ?$ $? ?$解:設(shè)分配挖土\ x\ 人,運土\ y\ 人,根據(jù)題意列方程組得$? ?$\left\{\begin{array}{l}x+y=44 \\6 x=5 y\end{array}\right.解得\left\{\begin{array}{l}x=20 \\y=24\end{array}\right.$? ?$答:分配 20 人挖土、 24 人運土才能使挖出的土及時運出。$? ?$ $? ?$解:設(shè)藥品包裝盒的寬為\ x \mathrm{~cm} , 高為\ y \mathrm{~cm} , 長為\ (x+4) \mathrm{cm} .\ $? ?$根據(jù)題意, 得\ \left\{\begin{array}{l}2 x+2 y=14, \\ (x+4)+2 y=13 .\end{array}\right.\ 解得\ \left\{\begin{array}{l}x=5, \\ y=2 .\end{array}\right.\ \ $? ?$所以\ V=5 \times 2 \times 9=90\left(\mathrm{~cm}^{3}\right) .$? ?$ $? ?$解:設(shè)用\ x \mathrm{~m}^{3}\ 木料做桌面, 則用\ y \mathrm{~m}^{3}\ 木料做桌腿, 恰好配成方桌$? ?$根據(jù)題意, 列二元一次方程組得:$? ?$\left\{\begin{array}{l}4 \times 50 x=300 y \\x+y=5\end{array}\right. \text { 解得 }\left\{\begin{array}{l}x=3 \\y=2\end{array}\right. \\$? ?$50 \times 3=150 \text { 張 }$? ?$\ \therefore\ 用\ 3 \mathrm{~m}^{3}\ 木料做桌面, 用\ 2 \mathrm{~m}^{3}\ 木料做桌腿, 恰好配成方桌 150 張.$? ?$ $?
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