Answer:
it's 5 because 20 -15 is 5
i think the answer to this problem is49
I think it would be around 7 lbs
(i could be wrong but i think this is about right)
Let the full marks = x
Then, it would be: x*40/100 = 60
x = 6000/40
x = 150
Full marks will be 150
You would expand becausee it isn't equal to anything
(x+3)^3=(x+3)(x+3)(x+3)
we can use binomial theorem or pascal's triangle
anyway, pascal's triangle is more practicl for this one
so
for the 3rd power

a=x
b=3

=