5а+7б-2а-8б

To simplify the expression \( 5a + 7b - 2a - 8b \), you can combine like terms:

1. Combine the terms with \( a \): \[ 5a - 2a = 3a \]

2. Combine the terms with \( b \): \[ 7b - 8b = -1b \quad \text{or} \quad -b \]

Now, put the combined terms together: \[ 3a - b \]

So, the simplified expression is: \[ 3a - b \]