(12+18):1,2

To simplify the expression \( (12 + 18) : 1.2 \), first, perform the addition:

\[ 12 + 18 = 30 \]

Now, divide by \( 1.2 \):

\[ 30 : 1.2 = \frac{30}{1.2} \]

To calculate \( \frac{30}{1.2} \), you can either perform the division directly or multiply the numerator and denominator by 10 to make it simpler:

\[ \frac{30 \times 10}{1.2 \times 10} = \frac{300}{12} \]

Now, divide \( 300 \) by \( 12 \):

\[ 300 \div 12 = 25 \]

Thus, \( (12 + 18) : 1.2 = 25 \).