Question 1166076
one half of the sum of b and 4 plus the product of 7 and n

would this be; 
(b+4)+(7xn)
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Don't use x for multiply, use * (Shift 8)
{{{((b+4)+(7*n))/2}}} is one possibility.
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{{{(b+4)/2 + 7n}}} is another.