Answer:6.9
Step-by-step explanation: Firstly we start of by opening the bracket to give 5z+8+4z+20=90, then we bring like terms together 5z+4z+8+20=90
to give us 9z+28=90, we bring 28 to the right side 9z=90-28, 9z=62, we then divide both sides by 9 to finally give z=6.88888888,but we round it up to 6.9