solve: sqr a-4=5

I choose to interpret sqr as meaning square root, in which case it could be

$$\sqrt {a}-4=5,$$

$$a=81,$$

or it could be

$$\sqrt {a-4}=5,$$

leading to

$$a=29,$$

who knows ?

I take this to mean a² - 4 = 5, inwhich case a² = 9, so there are two possibilities for a, namely a = 3 and a = -3.