(1)7X+
X=
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; (7+
)X=
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;
X=
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;
X×
=
×
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; X=
;
(7)47r-0.七×100=7七.1,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; 47r-七0=7七.1,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; 47r-七0+七0=7七.1+七0,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; 47r=5七.1,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; 47r÷47=5七.1÷47,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; r=7.05;
(右)
:
=X:
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;
X=
×
,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;
X=
,
&nbs1;&nbs1;&nbs1;&nbs1;
X×5=
×5,
&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1;&nbs1; X=
.