1.Diketahui ac+ad+bc+bd sm dg 68 dan c+d sama dg 4.Berapa nilai dari a+b+c+d..?

ac + ad + bc + bd = 68
a ( c + d ) + b (c + d ) = 68
( a + b ) ( c + d ) = 68
( a + b ) . 4 = 68
( a + b ) = 68 / 4
a + b = 17

a + b + c + d = 17 + 4
                    = 21