2 1/3:(5/8-8/3)-2* 1 3/7=7/3:(-49/24)-20/7=-168/147-20/7=(-168-420)/147=-588/147= -4
437-(x-83)=20
х-83=437-20
х-83=417
х=417+83
<span>х=500</span>
<em>1) 1/3-1/4=(4-3)/12=1/12</em>
<em>2) 1/3+1/4=(4+3)/12=7/12</em>
<em>3) 1/12 : 7/12=(1/12) * (12/7)=(1*12) : (12*7)=1</em><em>/7</em>
<em> </em>