Answer
calculate the longevity for the giraffe.
To prove
Let us assume lifespan of a guinea pig = u
Let us assume lifespan of a giraffe = v
Let us assume lifespan of a tiger = w
As given
The lifespan of a guinea pig is 6 years less than that of a giraffe.
The lifespan of a tiger is 4 times that of the guinea pig.
Than
u = v - 6
w = 4u
As given
total lifespan of the animals is 30 years.
than the equation becomes
u + v + w = 30
put the u = v - 6 ,w = 4u in the above equation
v - 6 + v + 4u = 30
put u = v - 6 in the above equation
v-6 + v + 4 × (v - 6) = 30
v - 6 + v + 4v - 24 = 30
6v = 30 + 24 + 6
6v = 60

v = 10 years .
Therefore the longevity for the giraffe is 10 years .