1) 3x-5y = 2k2x+7y = k-18x =-y can solve the small tent x big tent y problem 3x+x =100y = 200160x+400y = 96000, X = +8 < 6 (X- 1)+7 simplified X)-3 minimum value X=-2 instead of 2X-aX = 13 or 4, the 8 X value is greater than 10 yuan is greater than 5km (17.2-10). The distance from a to b is 10km ~ 10km, which can be greater than 10km.