Answer:
186.3
To find the answer you have to do inverse operations
9×20.7=186.3
186.3÷20.7=9
Ni : Zn: Cu = 7:2:9 =7x : 2x : 9x
7x+2x+9x = 3.8
18x=3.8
x=3.8/18=1.9/9≈0.21
Ni: 7x=7*0.21=1.47 ≈1.5 kg
Zn: 2x=2*0.21=0.42≈0.4 kg
Cu: 9x=9*0.21=1.89 ≈1.9 kg
Check 1.5+0.4+1.9 =3.8 True
Answer:
D. x2 + x - 20.
Step-by-step explanation:
(x – 4)(x + 5).
= x(x + 5) -4(x + 5).
= x2 + 5x – 4x – 20.
= x2 + x - 20.
Answer:
There is a total 50 questions.
Step-by-step explanation:
Let x = total questions in the exam
Since 82% of the test was scored correctly, that means 18% of the student's exam was scored incorrectly.
With this information we can write:
(Given that the student made 9 mistakes)
(divide 18% on both sides)

∴ There was a total of 50 questions in the examination.