Question

If A+D=117kg , A+M=88kg and M+D=161kg whats there total weightthx in advance

Answer 1

Think of A as a constant - with D it's 117 and with M it's 88

So the difference between D and M is 29   (117-88)

We also know that M + D = 161

Let's substitute in the problem  We will leave M equal to M and rewrite D as M+29 since it is 29 kg heavier.
M + M + 29 -161  or 2M +29 = 161 Subtracting 29 from both sides we get 2M=122
Now divide both sides two and get M=61
Since D is M+29 it is 61+29 or 100kg
Finally A + M = 88   A + 61 - 88   Subtract 61 from both sides and get A=17
So there you have it:
A=17kg
M=61kg
D=100kg and it works in all three equation in your problem (try it to check)

Answer 2

There's actually a really slick solution to this problem. Add all three equations. This results in 2(A+M+D)=366. Dividing by two, we see that A+M+D=183, so 183 is the total of the weights.