Answer:
Diagonals of a rhombus intersect at right angles
Therefore, [tex]\angle AOD=90[/tex]
[tex]Now,in\: \bigtriangleup AOD[/tex]
[tex]\angle OAD+\angle AOD+\angle ADO=180[/tex]
[tex]x+90+3x+12=180[/tex] [tex]\leftarrow [combing \: like\: terms][/tex]
[tex]4x+102=180\\-102 \: -102[/tex] [tex]\leftarrow [subtracting \:102 ][/tex]
[tex]\frac{4x}{4} =\frac{78}{4} \leftarrow [dividing \: by\: 4][/tex]
[tex]x=19.5[/tex] [tex]\Longleftarrow[/tex]
OAmalOHopeO
