4 2/7 - а = 1
а = 4 2/7 - 1
а = 3 2/7 ..........................
X+2/2-x=2
x+1-x=2
x-x=2-1
0=1
1) 4 + (-10) = 6
4 - 10 = -6
-(10-4)=-6
-6=-6
2) -7.5 + 3.5 = -4
-(7.5-3.5)=-4
-4=-4
3) -12.1+5.1=-7
-7=-7
4)7.8 + (-2.8)=5
7.8-2.8=5
5=5
5) -3.4+(-4.6)=-8
-3.4-4.6=-8
-(3.4+4.6)=-8
-8=-8
6) -1.25+(-1.75)=-3
-3=-3