exam Maths Puzzle Numerical Ability

please solve the problem for me.
nC0.nCn + nC1.nCn-1 + nC2.nCn-2 + ...........+nCn.nC0=(2n!)/(n!)^2

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exam Other Question

What is -y + 10 = 25? I did:
-y + 10 = 25
-25 -25
-y = -15
-1(-y) = -1(-15)
y = 15
Am I right? write the slop-intercept form of the equation of the line passing through the point (6,2) and with slop M= -4.