Change these fractions into decimal fractions.

The decimal fraction is $\boxed{0.4}$.

b)

The decimal fraction is $\boxed{0.2}$.

c)

The decimal fraction is $\boxed{0.5}$.

d)

The decimal fraction is $\boxed{0.37}$.

e)

The decimal fraction is $\boxed{0.19}$.

f)

The decimal fraction is $\boxed{0.25}$.

Write a plus and minus sum for each of the following, using the green and red shaded squares.

a)
The image already provides the sums for this part.
Addition: $\frac{2}{10} + \frac{8}{10} = \frac{10}{10}$
Subtraction: $\frac{10}{10} - \frac{8}{10} = \frac{2}{10}$

b)

There are 4 green squares and 3 red squares out of 10 total.

Addition: $\boxed{\frac{4}{10} + \frac{3}{10} = \frac{7}{10}}$
Subtraction: $\boxed{\frac{7}{10} - \frac{3}{10} = \frac{4}{10}}$

c)

There are 5 green squares and 2 red squares out of 10 total.

Addition: $\boxed{\frac{5}{10} + \frac{2}{10} = \frac{7}{10}}$
Subtraction: $\boxed{\frac{7}{10} - \frac{2}{10} = \frac{5}{10}}$

d)

There are 30 green squares and 60 red squares out of 100 total.

Addition: $\boxed{\frac{30}{100} + \frac{60}{100} = \frac{90}{100}}$
Subtraction: $\boxed{\frac{90}{100} - \frac{60}{100} = \frac{30}{100}}$

e)

There are 50 green squares and 40 red squares out of 100 total.

Addition: $\boxed{\frac{50}{100} + \frac{40}{100} = \frac{90}{100}}$
Subtraction: $\boxed{\frac{90}{100} - \frac{40}{100} = \frac{50}{100}}$