Срочно помогите, 2,3,5,7

Question

Срочно помогите, 2,3,5,7

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Answer 1

2)-6a+3.6b+0.9b+2.8a=-3.2a+4.5b
3)-6.3m+9-5.2+2.6m=-3.7m+3.8
5)R+0.48n-R+0.54n=n
7)2.4x-2.1y-2.4x+1.8y=-0.3y