7x-7=4x-1.
7x-7=4x-1,
7x-7+7=4x-1+7,
7x-4x=4x+6-4x,
3x=6,
3x÷3=6÷3,
x=2.
I ()you a happy birthday.
A.hope
B.want
C.expected
D.wish
粘土岩有泥岩、页岩、粉砂岩等。