3/4=x/12⇒x=12*3/4⇒x=9
y/2=17/5⇒y=2*17/5⇒y=34/5
3/4=18/x⇒x=18*4/3⇒x=24
0.8/0.5=5/x⇒x=0.5*5/0.8⇒x=3.125
3x/2=15/7⇒3x=15*2/7⇒x=15*2/21⇒x=10/7
2.1(3)/x=1.6/0.75⇒x=2.1(3)*0.75/1.6⇒x=192/90*0.75/1.6⇒x=1
pe acesta nu l inteleg cum vine, nu ca si rezolvare ci ca si editare a ex.