Oliver task calculation

Oliver calculated 12 tasks correctly, which was 8 more than the ones he calculated incorrectly.
a) How many problems did Oliver get wrong?
b) How many problems did he solve in total?

Final Answer:

b =  4
n =  16

Step-by-step explanation:

$$\begin{gathered} a=12 \\ a=8+b \\ b=a-8=12-8=4 \end{gathered}$$

$n=a+b=12+4=16$

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