the time failure in months X, of the light bulbs produced at two manufacturing plants A and B obey, respectively the following PDFs
for A: Fx(x) = ( 1 - e(-x/5))u(x)
for B: Fx(x) = ( 1 - e(-x/2))u(x)
plants B produced three times as many bulbs as plant A. the bulbs indistinguishable to the eye, are intermingled and sold. What is the probabilty that bulbs purchased random will burn at least.
2 months, 5 months, 7 months

What is the definition of Fx(x) and u(x)?

Is that Fx(x) supposed to be F_{x}(x) and the u(x) supposed to be {\mu}(x)?

What is the definition of Fx(x) and u(x)?.

Is that Fx(x) supposed to be F_{x}(x) and the u(x) supposed to be {\mu}(x)?.

Fx(x) ~ F_{x}(x)
u(x) just ignore it
thanks