The figure appears to be an irregular hexagon, and the perimeter is found by simply adding the length of its sides. Because there are variables, or indeterminates, amongst these, we need to group similar terms together: 7+2x+4z+8+3x+5z=15+5x+9z, (that is: 7+8=15, 2x+3x=5x, 4z+5z=9z). The expression 15+5x+9z represents the perimeter and cannot be reduced further, although brackets can be used where there is a common factor: 5(3+x)+9x, or 3(5+3z)+5x.
