Explanation:
A student solving for the acceleration of an object has applied appropriate physics principles and obtained the expression :
[tex]a=a_1+\dfrac{F}{m}[/tex]
Where
[tex]a_1=3\ m/s^2[/tex]
[tex]F=12\ kg-m/s^2[/tex]
m = 7 kg
So, the correct step for obtaining a common denominator for the two fractions in the expression in solving for a is (a) and the value of a is :
[tex]a=3+\dfrac{12}{7}[/tex]
[tex]a=4.71\ m/s^2[/tex]
Hence, the correct option is (a).