Addieren und subtrahieren mit Variablen

Berechne!

m + 2m = 5x + 3x =
3s + s + 4s = 2u + 4u + 3u =
1,2a + 3,5a = 0,3e + 12,1e + 2,7e =

7s - 4s = 8x - 13x =
4m - 12m = 6a - a - 5a =
12,7u - 11,3u = 60,3t - 15,5t =