log_2 6 - log_2 15 + log_2 20 = 3.
To simplify the expression log_2 6- log_2 15 + log_2 20, you can use logarithmic properties.
The subtraction of logarithms can be expressed as the division of the corresponding numbers, and the addition can be expressed as the multiplication of the corresponding numbers.
log_2 6- log_2 15 + log_2 20
= log_2 (6/15 ×20)
= log_2 (2/5 × 20)
= log_2 (40/5)
= log_2 8
= log_2 2^3
= 3
so, log_2 6- log_2 15 + log_2 20 = 3.