Help pzhzhzhzh! very urgently it is necessary. if it is possible, then it is desirable in detail) figures 2.3 and 4

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1 is possible more simply)-2+(-4)+ (-6)+ (-8)=-2-4-6-8=-20 2)-3+(-5)+ (-7)+ (-9)=-3-5-7-9=-24 3) we watch what numbers are divided into 3: 3,6,9,12,15,18.... We look for a trial and error method of a tsisl-12+(-15)+ (-18)=-12-15-18=-45 generally already explained, there is no sense already simply) 2. 2 4 6 8 of X + x +2+ x +4+ x +6=20 4th +12=20 4th =8 X =2 first, each following +2 3. 3 5 7 9 of X + x +2+ x +4+ x +6=24 the 4th +12=24 4th =12 X =3, each following number +2 4. 12 15 18 X+ x +3+ x +6=45 the 3rd +9=45 3rd =36 X =12 first, following +3
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