78+7x+45+8x

To simplify the expression \( 78 + 7x + 45 + 8x \), you can combine like terms.

Combine the constant terms (78 and 45) and the terms with \( x \) (7x and 8x):

1. Constants: \( 78 + 45 = 123 \)
2. Terms with \( x \): \( 7x + 8x = 15x \)

Putting it all together, the simplified expression is:

\[ 123 + 15x \]