What is halfway between positive 6900 and negative 8100?

Parks is wearing several rubber bracelets one third of the bracelets are tie-dye 1/6 are blue and 1/3 of the remainder are camouflage if parks wears 2 camouflage bracelets how many bracelets does he have on

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

Which is the focus of a parabola with equation y2=4x