Solve the following systems of linear equations: 1. x+y=-1, 2x-y=-3 2. 3x+y=7, 6x−y=25 3. 3x+2y=8, 2x−y=3

$$
(x+y) + (2x-y) = -1 + (-3)
$$
$$
3x = -4
$$
$$
x = -\frac{4}{3}
$$

$$
-\frac{4}{3} + y = -1
$$
$$
y = -1 + \frac{4}{3}
$$
$$
y = -\frac{3}{3} + \frac{4}{3}
$$
$$
y = \frac{1}{3}
$$
The solution is:
$$
\boxed{x = -\frac{4}{3}, y = \frac{1}{3}}
$$

$$
(3x+y) + (6x-y) = 7 + 25
$$
$$
9x = 32
$$
$$
x = \frac{32}{9}
$$

$$
3\left(\frac{32}{9}\right) + y = 7
$$
$$
\frac{32}{3} + y = 7
$$
$$
y = 7 - \frac{32}{3}
$$
$$
y = \frac{21}{3} - \frac{32}{3}
$$
$$
y = -\frac{11}{3}
$$
The solution is:
$$
\boxed{x = \frac{32}{9}, y = -\frac{11}{3}}
$$

$$
2(2x-y) = 2(3)
$$
$$
4x-2y=6 \quad (3)
$$

$$
(3x+2y) + (4x-2y) = 8 + 6
$$
$$
7x = 14
$$
$$
x = 2
$$

$$
2(2) - y = 3
$$
$$
4 - y = 3
$$
$$
-y = 3 - 4
$$
$$
-y = -1
$$
$$
y = 1
$$
The solution is:
$$
\boxed{x = 2, y = 1}
$$

$$
3(3x+2y) = 3(7) \Rightarrow 9x+6y=21 \quad (3)
$$
$$
2(4x+3y) = 2(15) \Rightarrow 8x+6y=30 \quad (4)
$$

$$
(9x+6y) - (8x+6y) = 21 - 30
$$
$$
x = -9
$$

$$
3(-9) + 2y = 7
$$
$$
-27 + 2y = 7
$$
$$
2y = 7 + 27
$$
$$
2y = 34
$$
$$
y = 17
$$
The solution is:
$$
\boxed{x = -9, y = 17}
$$

$$
x + (3x) = 72
$$
$$
4x = 72
$$
$$
x = \frac{72}{4}
$$
$$
x = 18
$$

$$
y = 3(18)
$$
$$
y = 54
$$
The two numbers are:
$$
\boxed{18 \text{ and } 54}
$$

$$
(G+8) + G = 32
$$
$$
2G + 8 = 32
$$
$$
2G = 32 - 8
$$
$$
2G = 24
$$
$$
G = \frac{24}{2}
$$
$$
G = 12
$$

$$
B = 12 + 8
$$
$$
B = 20
$$
The number of boys in the class is:
$$
\boxed{20 \text{ boys}}
$$