[(7/15)-(3/40)-(1/24)]÷0,7=[((7×16-3×6-1×10)/240)]÷0,7=[(112-18-10)/240]÷0,7=[(112-28)/240]÷0,7=[(84/240)]÷0,7=(84/240)÷(7/10)=(84/240)×(10/7)=(84×10)/(240×7)=(12×7×10)/(12×2×10×7)=(1/2)=0,5.
4*3x=18
12x=18
x=18/12
x=1.5
42/7=6
6/1.5=4
19-7=12 15-6=9 12-9=3 разность- это минус
1. 2/3 - 1/15 + 4/5 = 10/15 - 1/15 + 12/15 = 21/15 = 7/5 = 1,4
2. (180 - 120) : 180 = 60/180 = 1/3