Respuesta :

a=20-b (1)
1.5a+1.25b=28 (2)
Sub 1 into 2
1.5(20-b)+1.25b=28
30-1.5b+1.25b=28
-0.25b=28-30
-0.25b=-2
b=-2/-0.25
b=8
—————-
a=20-8
a=12
A= 12 and B= 8
Because 1.5•12= 18 so then take 1.25•8= 10 then add 18+10 which equals 20 when added together