Answer and Explanation:
To find : Perform the indicated operations?
Solution :
Modular math is defined as

or 
Where, A is the dividend
B is the divisor
Q is the quotient
R is the remainder
The solution is 
Now, We perform same in every case
1) 
We can direct add the term,

Now, we divide 15 by 5 and see the remainder

Remainder is 0.
So, 
2) 
We can direct subtract the term,

Now, we divide -4 by 12 and see the remainder

Remainder is 8.
So, 
3) 
We can direct multiply the term,

Now, we divide 12 by 5 and see the remainder

Remainder is 2.
So, 
4) 
We can direct divide the term,

Now, we divide 0.5 by 5 and see the remainder

Remainder is 0.5.
So, 