Question

find the value of k which has unique solution 3x+5y =12 and 4x-7y=k

Answer 1

3x+5y=12
3x=12-5y
x=12-5y/3
now,
4x-7y=k
put the value of x
4x-7y=k
4(12-5y/3)-7y=k
48-20y