Do a two column proof!
given: ab = dc
prove: ac = db
!

AC       =        DB     (Proved)

Step-by-step explanation:

Here, in the triangle ADE

AB = DC (Given)

Now, by EUCLID's LEMMA

If equals are added  to equals, the sum  are equal.

⇒   AB   +   BC   =   DC   +   BC

or,         AC       =        DB    

                 Hence Proved!

b. x- 48 =120

step-by-step explanation:

to find the perimeter of the rectangle this is the expression:

x-9+x-9+3x-4+3x-4=138

if we simplify it:

8x-26=138

remember, 138 is what it all adds up to

the length is 11.5cm

the width is 57.5cm

the area is 661.25cm^2

the answers might not be correct use at own risk