—How do you usually come to school, by bus or by bike?
— . I walk.
如图是排卵、受精、受精卵发育、植入子宫内膜的连续过程,试回答下列问题.
甲乙两人同时解方程组ax+by=2cx-7y=8时,甲正确解得x=3y=-2,乙因抄错c而解得x=-2y=2,则a,c的值是( )