Question

5. Find the value of x in the given figure,
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Answer 1

name each vertices, A,B and C, such that A= 4x+3

B=81° and C= 42°

Now draw another line D from B to the bottom such that ABD is a straight line.

Now, L DBC + CBA= 180 ( straight line)

L DBC= 180-81°= 99°

In ∆ DBC,

L DBC+L BCD+ L CDB= 180°

L CDB+ 99+ 42= 180

L CDB= 180-141= 39°

Let the upper line be AF

So, LCDB +LBAF= 180 ( alternate opposite)

39° +L BAF= 180

L BAF= 180-39= 141

And we know, LBAF (interior) + LBAF (exterior)

= 360

141+ (4x+3)= 360

4x+3= 360-141

4x= 319-3

x= 316/4 = 79