Question 309381
"I do not have a very large understanding of logarithms, and i can't solve the question:
log 7 + log x = 2
(The answer is 100/7)
I can solve things such as log x - log 6 = log 15 without having to worry about the base 10, but i do not understand when i need to use it to get the right answer."

log 7 + log x = 2
means
log10 7 + log10 x = 2
the 10 is your base (b)
logarithmic rule: logb (mn) = logb (m) + logb (n)
so we have
log10 (7x) = 2
logarithmic rule: logb (y) = x is equivalent to b^x = y
so we have
10^2 = 7x
100 = 7x
100/7 = x
hope this helps