I am doing sums.
I am doing sums.
Explanation
Present Continuous Tense
Active Voice: Subject + is/am/are + First of verb + ing + obect.
Passive Voice: Object + is being/am being/ are being + third form of verb + by + subject.
Active Voice: I am doing sums.
Passive Voice: Sums are being done by me.
Do is a regular verb which means کرنا
Do means perform.
Did is the second form while done is the third form of Do.