a = ?

b = 12
c = 15
c2-b2=a2

By using the Pythagorean theorem formula, we can calculate the value of 'a':

a^2 = c^2 - b^2
a^2 = 15^2 - 12^2
a^2 = 225 - 144
a^2 = 81

Taking the square root of both sides, we get:

a = √81
a = 9

Therefore, the value of 'a' is 9.

To find the value of `a`, we can use the given equation: `c^2 - b^2 = a^2`.

First, substitute the values of `b` and `c` into the equation:
`c^2 - b^2 = a^2`
`(15)^2 - (12)^2 = a^2`

Simplify the equation:
`225 - 144 = a^2`
`81 = a^2`

To solve for `a`, take the square root of both sides:
`√81 = a`
`9 = a`

Therefore, the value of `a` is 9.

To find the value of variable 'a', we can use the given equation: c^2 - b^2 = a^2, where c is 15 and b is 12.

First, let's substitute the values of c and b into the equation:
15^2 - 12^2 = a^2

Next, we calculate the square of each number:
225 - 144 = a^2

Now, subtract the two values:
81 = a^2

To find the value of 'a', we need to take the square root of both sides of the equation:
√81 = √(a^2)

The square root of 81 is 9, so:
9 = a

Therefore, the value of variable 'a' is 9.