Let's solve each equation one by one:

1) (52-x) + 43 = 78
52 - x + 43 = 78
95 - x = 78
-x = 78 - 95
-x = -17
x = 17

2) 123 - (37 + a) = 15
123 - 37 - a = 15
86 - a = 15
-a = 15 - 86
-a = -71
a = 71

3) 169 + (37 + a) = 235
169 + 37 + a = 235
206 + a = 235
a = 235 - 206
a = 29

4) (52 + x) + 43 = 178
52 + x + 43 = 178
95 + x = 178
x = 178 - 95
x = 83

5) 354 - (177 + a) = 93
354 - 177 - a = 93
177 - a = 93
-a = 93 - 177
-a = -84
a = 84

So, the solutions to the equations are:
1) x = 17
2) a = 71
3) a = 29
4) x = 83
5) a = 84