$v_f = v_i + at$

$7.32 = v_o + 10a$ → equation (1)

$5.49 = v_o + 12a$ → equation (2)

Equation (1) minus equation (2)

$1.83 = -2a$

$a = -0.915 \, \text{ m/sec}^2$ *answer*

From equation (1)

$7.32 = v_o + 10(-0.915)$

$v_o = 16.47 \, \text{ m/sec}$ *answer*