Solve by substitution: 4a - b = 1, 9a - b = -3, a - b = -6

From the third equation, we can solve for a in terms of b:

a = b - 6

Now we can substitute this expression for a into the first two equations:

4(b - 6) - b = 1
9(b - 6) - b = -3

Expanding and simplifying:

4b - 24 - b = 1
9b - 54 - b = -3

Combining like terms:

3b - 24 = 1
8b - 54 = -3

Adding 24 to both sides of the first equation and adding 54 to both sides of the second equation:

3b = 25
8b = 51

Dividing by 3 and 8 respectively:

b = 25/3
b = 51/8

Now that we have the value of b, we can substitute it back into the equation a = b - 6 to find the value of a:

a = 25/3 - 6
a = 25/3 - 18/3
a = 7/3

Therefore, the solution to the system of equations is a = 7/3 and b = 25/3.

The third equation can be rewritten as a = b - 6. We can substitute this into the first two equations to get:

4(b - 6) - b = 1
9(b - 6) - b = -3

Simplifying the first equation:

4b - 24 - b = 1
3b = 25
b = 25/3

Substituting this back into the equation a = b - 6:

a = 25/3 - 6
a = -7/3

So a = -7/3 and b = 25/3

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