- 3.9 + (1.2) + (- 6.1) + (+2.8)=?3) - 7/12 + (+1/8) + (-5/12) + (+3/4)=?

1) [latex]-3,9+1,2-6,1+2,8=(-3,9-6,1)+(1,2+2,8)=-10+4=-6[/latex] 2) [latex] -\frac{7}{12}+ \frac{1}{8}- \frac{5}{12}+ \frac{3}{4}=(-\frac{7}{12}- \frac{5}{12})+(\frac{1}{8} + \frac{3}{4})=-1+( (\frac{1}{8} + \frac{6}{8})=-1+ \frac{7}{8} [/latex][latex]=- \frac{1}{8} [/latex]