Question

Can someone answer this question

Answer 1

AC = BD ( Given )

AC - BC = BD - BC ( if equals are subtracted from equals then results are equal)

AB = CD ..

Hence, proved..

Answer 2

it is given that , AC = BD 
From the figure,
AC = AB + BC
BD = BC + CD    
⇒ AB + BC = BC + CD 
According to Euclid's axiom, when equals are subtracted from equals, remainders are also equal. 

Subtracting BC both sides,
AB + BC - BC = BC + CD - BC
AB = CD