For example you have 2 Assignments. One is 86/100 pts possible with a Factor of 1 and another is 45/50 pts possible with a Factor of .5.

1x86=86 (because this is based on 100 pts we dont need to convert it)
for the 45/50 pts we need to divide 45/50 to get the % 45/50=.9 which is 90%
So .5x90=45
45+86(total points added together)=131
1+.5(total weights added together)=1.5
131/1.5=87.33 grade

Take the same example and change the second assignment to a factor of 1
1x86=86 (because this is based on 100 pts we dont need to convert it)
for the 45/50 pts we need to divide 45/50 to get the % 45/50=.9 which is 90%
so 1x90=90
90+86(total points added together)=176
1+1(total weights added together)=2
176/2=88 grade