$25a + $15s =$305
a + s = 17
a = 17 - s
$25a +$15s =$305
$25(17-s) + $15s=$305
425-25s +15s = $305
425-10s=305
-10s=305-425
-10s= -120
-10s/-10 = -120/-10
s = 12
a+ 12 = 17
a = 5
Check
$25a + $15s =$305
$25(5) + $15(12) =$305
125 + 180 = 305
305 = 305
1.) 3 + 2 x 10 = 3 + 20 = 23
2.) 2(1-4)^2 = 2(-3^2) = 2(9) = 18
3.) -3^2 + 3^2 = 9 + 9 = 18
4.) 8 - [(4-7) + (8-1)] = 8 - [-3 + 7] = 8 - 4 = 4
5.) 4 - {8 - (2-4)} = 4 - {8 - (-2)} = 4 - {8 + 2} = 4 - 10 = -6