After eating 15 green macaroons, the number is reduced to 40 green macaroons - 15 green macaroons = 25 green macaroons
If Fran ate 15 green macaroons, he also ate 2 red/green * 15 green macaroons = <<15*2=30>>30 red macaroons.
The total number of red macaroons remaining is 50 red macaroons - 30 red macaroons = <<50-30=20>>20 red macaroons
The total number of macaroons Fran has left are 20 macaroons + 25 macaroons = <<20+25=45>>45 macaroons
#### 45