15÷20= 78÷26= 26÷4=
30÷7= 91÷13= 18÷21=
① x+=
②2x-(+)=
③+-x=1
- = + = + = 1- =
- = + = + = - =
① - +
② -( - )
③ + +
④8.11- +2.89-
①a+a ②5a ③a2 ④6a ⑤a+7