Answer:
d=-13
Explanation:
Let's solve your equation step-by-step. 
−7(6+d)=49 
Step 1: Simplify both sides of the equation. 
−7(6+d)=49 
(−7)(6)+(−7)(d)=49(Distribute) 
−42+−7d=49 
−7d−42=49 
Step 2: Add 42 to both sides. 
−7d−42+42=49+42 
−7d=91 
Step 3: Divide both sides by -7. 
−7d−7=91−7 
d=−13
Hope this helps have an amazing day :))