It depends where you want the parentheses:
15 + (26 x 10) = 275
(15 + 26) x 10 = 410
15 +26+9+12
26 x 15 = 390 It is easy to work out because 26 x 10 = 260 and 26 x 5 = 130 then simply add 260 to 130.
26 with remainder 10.
1.5 + 2.6 = 4.1 3/2 = 15/10 13/5 = 26/10 15/10 + 26/10 = 41/10 = 4 and 1/10
-26
39, 26 and 30
10/270 + 15/270 + 27/270 = 52/270 = 26/135
9/30 + -26/30 = -17/30
400 ÷ 15 = 26
-41
26 times 12 +5= 317
9 + 26 + 61 + 8 + 18 + 44 + 10 + 90 = 266