a = log 80
b = log 45
log 80 = log (8 * 10 ) = log 8 + log 10 = log ( 8 ) + 1 = a
log 45 = log ( 4.5 * 10 ) = log 4.5 + log 10 = log ( 4.5) + 1 = b
So
a - 1 = log 8
b - 1 = log 4.5
(a - 1) + (b - 1) = log 8 + log 4.5
(a + b) - 2 = log (8 * 4.5)
(a + b) - 2 = log 36
