PLS be quick and answer as best as you can The following equation was written on the chalkboard: Δ + Δ + ◊ + Ꙫ ─ Δ = Ω. If Δ = 4, Ꙫ = 3 and Ω = 12, what is the value of ◊?

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)