why is 15/5(8-6+3)*5=75 instead of 3

The rule is number next to brackets without any sign in between is part of brackets and is multiplied with equation in the brackets.

so 5(8-6+3) will be solved altogether first.

why would it be 3? 

because of order of operations

The way it is written says this:

15/5    x  (8-6+3)  x 5

3         x    (5)        x 5    = 75

but when you apply rule of bodmas to solve the equation you will have to solve  brackets, Order,Division, Multiplication, Addition, Substraction.

so it will solve as 

15/5(8-6+3)*5=

15/ 5(5)*5

15/25 *5

0.6*5

=3 answer 

But what rule is applied to bring answer = 75 

15/5(8-6+3)*5=

5right next to bracket is part of the bracket so it cannot be read as  15/5    x  (8-6+3)  x 5 it will be read as 

15/ 5(5)*5 which is 15/ 5x(5)*5

Let's take it like this.

You start with the parentheses (8-6+3) which equals 5.

Then, you have 15/5*5*5

Next, you go from left to right, which means 3*5*5, which equals 75. The lack of parenthes around the 3 fives means that it's not in a fraction, but just 15 divided by 5, times 5 times 5. 

because of your fat face losers