1. **State the problem:** We are given a straight line with two adjacent angles, one measuring 58° and the other labeled $t$. We need to find the value of $t$. 2. **Recall the rule:** Adjacent angles on a straight line add up to 180° because a straight line forms a straight angle. 3. **Write the equation:** $$58^\circ + t = 180^\circ$$ 4. **Solve for $t$:** $$t = 180^\circ - 58^\circ$$ 5. **Calculate:** $$t = 122^\circ$$ 6. **Answer:** The value of $t$ is $122^\circ$.