One way:

A1: 1
B1: 1
C1: =A1 + B1
D1: =3*A1 + 4*B1


Set Target Cell = D1
Equal to Value of 7
By changing cells: A1:B1
Subject to the Constraints: $C$1 = 1




In article ,
Mike wrote:

How to use Excel to solve for 2 unknown in linear equation, for eg,

x + Y = 1
3x + 4Y =7

Thanks
Mike