Find the first term of a GP

A geometric sequence follows the pattern:

$a, ar, ar^2, ...$ where $a$ is the first term and $r$ is the common ratio. Hence, in this case, we are asked to find the value of $a$ , knowing that:

$a = x$

$ar= 3.75$

$ar^2 = 5.625$

If we divide 5.625 by 3.75 we get the common ratio. = $\frac{3}{2}$

Then we divide 3.75 by the common ratio to get $a$ . = 2.5