Okay so this is how you solve this step by step.
2log7(5)+log7(x)=log7(100)
Subtract 2log7(5) from both sides
log7(x)=log7(100)-2log7(5)
Simplify log7(100)-2log7(5)
log7(x)=2log7(2)
Apply log rule: alogc(b)=logc(b^a)
log7(x)=log7(4)
x=4. <----Answer
I hope this helps.
