Evaluate (7012 - a) : b when a = 2148 and b = 4.

Step-by-step solution

1. 1

   Substitute and keep the bracket. The colon in $(7012-a):b$ is a division sign, so

   $(7012-2148)\div 4$

   The bracket is essential: without it, $7012-2148\div 4$ would mean $7012-537=6475$.

2. 2

   Do the subtraction inside the bracket. Column subtraction, borrowing once in the tens column:

   $7012-2148=4864$

   A fast sanity check: $2148+4864=7012$. ✓

3. 3

   Divide the result by $b=4$. Split $4864$ into parts that are easy to halve twice:

   $4864\div 4=(4800+64)\div 4=1200+16=1216$

4. 4

   Verify by multiplying back. $1216\times 4=4864$, which is exactly the numerator, and the division left no remainder. The value of the expression is $1216$.