Answer
$t = 0.72~s~~$ is the first time that the reference lines are momentarily aligned.
Work Step by Step
We can find an expression for the angular displacement of Disk A:
$\theta_A = (9.5~rad/s)~t$
We can find an expression for the angular displacement of Disk B:
$\theta_B = \frac{1}{2}(2.2~rad/s^2)~t^2 = (1.1~rad/s^2)~t^2$
We can find $t$ when Disk A has rotated a full rotation of $(2\pi~rad)$ more than Disk B:
$\theta_A = \theta_B+2\pi$
$9.5~t = 1.1~t^2+2\pi$
$1.1~t^2-9.5~t+2\pi = 0$
We can use the quadratic formula:
$t = \frac{9.5\pm \sqrt{(-9.5)^2-(4)(1.1)(2\pi)}}{(2)(1.1)}$
$t = \frac{9.5\pm \sqrt{62.6}}{(2)(1.1)}$
$t = 0.72~s, 7.9~s$
At $~~t = 0.72~s~~$ Disk A has completed one more full rotation than Disk B.
$t = 0.72~s~~$ is the first time that the reference lines are momentarily aligned.
