[tex]\displaystyle\bf\\\left \{ {{4u+5p=1 \ |\cdot(-5)} \atop {5u+7p=5 \ |\cdot 4}} \right. \\\\\\+\left \{ {{-20u-25p=-5} \atop {20u+28p=20}} \right. \\-----------\\3p=15\\\\p=15:3=5\\\\4u=1-5p=1-5\cdot5=1-25=-24\\\\u=-24:4=-6\\\\Otvet \ : \ u=-6 \ \ ; \ \ p=5[/tex]