two job taxes

Hi 

my name is Zahir 

with this struggling life specially in the last years ,I am thinking to get another job many of my coworkers they said is not worth it because the CRA will take  too much for the taxes and I find my self to pay back the government .

my question if i have a job for 40000 /year and the second job with 35000/year how to calculate approximately my refund to the government . 

they will consider it is 40000+35000 =75000 job or it have other (fine...)

in other way does a one job for a 75000/year is same when it have two jobs for 75000/year 

I appreciate your responses 

thanks