You need to find the value of c so solve the first equation in terms of y:

-4c + y = -9
y = -9 + 4c

then substitute the result (-9 - -4c) into the second equation:

5c + 9(-9 + 4c) = 4
5c + (9 x -9) + (9 x 4c) = 4
5c - 81 + 36c = 4
5c + 36c = 4 + 81
41c = 85
c = \( \frac{85}{41} \)
c = 2\(\frac{3}{41}\)

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 8cm + 6cm + 5cm = 19cm

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

6a + 7a = 13a

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

4a⁵ - 7a⁵ = -3a⁵