Look carefully at the sign for each question. Some are subtracting!

$$5.4 + 3.2 = 8.6$$

The answer is $\boxed{\text{8.6}}$.

$$8.7 - 2.5 = 6.2$$

The answer is $\boxed{\text{6.2}}$.

$$6.23 + 2.54 = 8.77$$

The answer is $\boxed{\text{8.77}}$.

$$7.85 - 3.41 = 4.44$$

The answer is $\boxed{\text{4.44}}$.

$$4.68 + 3.53 = 8.21$$

The answer is $\boxed{\text{8.21}}$.

$$9.14 - 4.62 = 4.52$$

The answer is $\boxed{\text{4.52}}$.

$$13.58 - 6.29 = 7.29$$

The answer is $\boxed{\text{7.29}}$.

$$11.75 + 5.68 = 17.43$$

The answer is $\boxed{\text{17.43}}$.

$$24.31 + 8.92 = 33.23$$

The answer is $\boxed{\text{33.23}}$.

$$15.04 - 7.36 = 7.68$$

The answer is $\boxed{\text{7.68}}$.