Here are the solutions to your questions.
3. Convert the recurring decimal 12.18 into fraction
Step 1: Let x be the recurring decimal.
x=12.18
Step 2: Multiply by 10 to move the non-repeating part to the left of the decimal point.
10x=121.8(∗)
Step 3: Multiply by 10 again to move one cycle of the repeating part to the left of the decimal point.
100x=1218.8(∗∗)
Step 4: Subtract equation (∗)