Could any expert answer the following question for me please?

Suppose we have two digital input frequencies in1 and in2 in the range of about a little less than or greater than 100 kHz each.

My objective is to add and subtract the two input frequencies to get an output frequency which is equal to out = in1 + in2 Hz or out = in1 - in2 Hz. I imagine that a prerequisite to get the right output is that both in1 and in2 must have equal pulse although in1 and in2 May have very different frequencies.

So:

1- if it’s is necessary to fix the pulse width, is there a trivial solution preferably a CMOS solution to fix the pulse width of one of the input frequencies to the pulse width of the other input frequency?

2- is there a trivial solution to get an output frequency which is the sum or the different of the two input frequencies?

Thank you