Solve for the integer values of x and y.

a)
[tex]\[
\begin{cases}
0.3x + 0.4y = 0.5 \\
x - 2y = -5
\end{cases}
\][/tex]

b)
[tex]\[
\begin{cases}
0.9x - 0.2y = 1.3 \\
x + y = 10
\end{cases}
\][/tex]

c)
[tex]\[
\begin{cases}
1.2x - 0.7y = -1.3 \\
4x - 5y = 9
\end{cases}
\][/tex]

Solve the following problem:

A car travels from point A to point B, a distance of 450 km, in 10 hours. During the trip, it travels 260 km per hour on a paved road and 30 km per hour on a dirt road. How much time does the car spend on the paved road and how much time on the dirt road?

Raúl and Esteban went to a stationery store to buy materials assigned to them.