Group 17. They combine with alkali metals and form salt, the are reactive, they have 7 electrons in their outer energy level
17+27
simplify the parenthesis
Answer:
Step-by-step explanation:
let x < 30 be the width of strip of lawn.
then (80-2x)(60-2x)=800
4800-160x-120x+4x²=800
4x²-280x+4000=0
x²-70 x+1000=0
x²-20x-50x+1000=0
x(x-20)-50(x-20)=0
(x-20)(x-50)=0
x=20,50
x=50(rejected)
x=20 m