25log625 - 3log21 + 3log7 - 5log6 + 5log30 =

^(5²)log5^4 - ^3log3³ + ^3log7 - ^5log6 + ^5log30
= 4/2 - 3 + ³log7 - (^5log6 - ^5log30)
= -1 - ³log7 - ^5log(6/30)
= -1 - ³log7 - ^5log5^-1
= -1 - ³log7 + 1
= -³log7
atau
= -(log7/log3)
= -1.77

25log625 = 5^2 log 5^4 
                = 4/2=2

3log3x7 x 3log7 = 3

5log6 x 5log 5x6 = 6

jadi 2-3-6 = -7

maaf kalau salah