To solve this equation, we need to find the value of x.

First, let's simplify the left side of the equation:

1/3 - 2/5 - 3x = 3/4

To combine the fractions, we need to find a common denominator. The least common multiple of 3 and 5 is 15.

Multiplying the first fraction by 5/5 and the second fraction by 3/3, we get:

(5/15) - (6/15) - 3x = 3/4

Now, we can combine the fractions:

(-1/15) - 3x = 3/4

Next, let's isolate the variable term by moving the constant term to the other side of the equation:

-3x = 3/4 + 1/15

To add the fractions, we need a common denominator. The least common multiple of 4 and 15 is 60.

Multiplying the first fraction by 15/15 and the second fraction by 4/4, we get:

-3x = 45/60 + 4/60

Combining the fractions, we have:

-3x = 49/60

Finally, let's solve for x by dividing both sides of the equation by -3:

x = (49/60) / -3

Dividing the fractions, we get:

x = -49/180

Therefore, the solution to the equation is x = -49/180.