Hey there!
2 3/4a = 19 1/4
11/4a = 77/4
MULTIPLY 4/11 to BOTH SIDES
4/11 * 11/4a = 4/11 * 77/4
CANCEL out: 4/11 * 11/4 because it gives you 1
KEEP: 4/11 * 77/4 because it helps solve for the a-value
NEW EQUATION: a = 4/11 * 77/4
SIMPLIFY IT!
a = 7
Therefore, your answer is: a = 7
Good luck on your assignment and enjoy your day!
~Amphitrite1040:)