text: log 90 + log(13/45) - log (8/13) + 4 log5\n= log (90 (13/45) )- log (8/13) +  log5^4\n= log (26 )- log (8/13) +  log5^4\n= log (26 /(8/13) ) +  log5^4\n= log ( 26(13)/8) + log 5^4\n= log (13(13) /4)  + log 5^4\n= log ( 13^2 5^4  /4)\n~