si: a/2 = b/3 = c/4; 2a+b-c=15
hallar "bc"
2a + b - c = 15
b = 15 + c - 2a
si
a/2 = b /3
3.a = 2.b
a = 2b/3
b = 15 +c - 2(2b/3)
b = 15 +c - 4b/3
b + 4b/3 = 15 +c
7b/3 = 15 + c b/3 = c/4 → c = 4b/3
7b/3 = 15 + 4b/3
7b/3 - 4b/3 = 15
3b/3 = 15
b = 15
entonces
a = 2b/3 → a = 2.15/3 → a = 10
c = 4b/3 → c = 4.15/3 → c = 20
así que
bc = 15 * 20
bc= 300
espero que te sirva, salu2!!!!