Question

2,1м-1,3= -2(0,4-1,8м)+2,5 пежжжжжжжжжж

Answer 1

$\displaystyle 2,1m-1,3=-2(0,4-1,8m)+2,5\\2,1m-1,3=-0,8+3,6m+2,5\\2,1m-1,3=1,7+3,6m\\2,1m-3,6m=1,7+1,3\\-1,5m=3\\m=-2$