We can substitute \( s \) (which is \( 4b \)) into the second equation \( s + b = 55 \).
Given:
- \( s = 4b \)
- \( s + b = 55 \)
Substituting \( 4b \) for \( s \) in the second equation:
\[ 4b + b = 55 \]
Combining like terms:
\[ 5b = 55 \]
Now, divide both sides by 5:
\[ b = \frac{55}{5} = 11 \]
So, \( b = 11 \).
Now, we can find \( s \) by substituting \( b \) back into the first equation:
\[ s = 4b = 4 \times 11 = 44 \]
Thus, Michael used 44 strawberries and 11 bananas for his smoothies.