Answer:
i guess you need to prove that right side is equal to the left side.
Step-by-step explanation:
R.H.S.
=(3×5) t + (21-12)
=(15)t + (9)
=15t+9
L.H.S.
=15t + 3²
=15t + 9
.: R.H.S. = L.H.S.
