lets denote the ten golf scores with: s1, s2, ..., s10 and let the lowest score be s1 = 68 and the highest score s10 = 80

the mean of Randy's last ten golf scores is 74

(s1 + s2 + .. + s10)/10 = 74 multiply both sides by 10

s1 + s2 + .. + s10 = 740

s2 + .. + s9 = 740 - (s1 + s10)

s2 + .. + s9 = 740 - (68 + 80)

s2 + .. + s9 = 592

the average score of the eight golf scores (after the lowest and highest score are thrown out) is:

(s2 + .. + s9)/8 = 592/8 = 74