Respuesta:
Explicación paso a paso:
M - S = D.....(1)
S = 2D.......(2)
M + S + D = 30....(3)
(1) en (3):
M + S + M - S = 30
2M = 30
M = 30/2
M = 15
M en (1) :
15 - S = D.......(4)
(2) en (4):
15 - 2D = D
15 = 2D + D
15 = 3D
15/3 = D
5 = D
S = 2D
S = 2(5)
S = 10