To solve the problem, get the percentage of each test by multiplying the score and the percentage then add it all up:
82 * .25 (highest test grade) + 65* .15 (lowest test grade) + 71*.20 (each test remaining) + 77*.20 (each test remaining) + 92*.20 (homework grade)
= 20.5 + 9.75 + 14.2 + 15.4 + 18.4 = 78.25 or 78% in whole number