Tolong kak dibantu nomer 1-4... sama caranya

1). gambar 1 =
2a+3a=90
5a=90
a=90/5
a=18
gambar 2=
46+a+29+5a+15=180
a+5a+46+29+15=180
6a+90=180
6a=180-90
6a=90
a=90/6
a=15