If i have an 86 and i don’t do a 50 point assignment, what will my grade be in the class?

Well you are at a 86% so this is considered a "B" grade on an average grade scale. If you take 50 points we would need to know the Total point you could have got in that class to be able to see how much a percent was the assignment work and then take that percentage of the assignment and subtract it from the 86% to see where on the scale you would fall in after the assignment points were taken off.   Hope this helps :)