Question 983162
.
x=years ago Charlie was 3/4 as old as Robert
.
70-x=3/4(78-x)
70-x=58.5-(3/4)x
11.5=(1/4)x
46=x
ANSWER: Charlie was 3/4 as old as Robert 46 years ago.
.
CHECK:
46 years ago, Charlie was (70-46=)24 and Robert was (78-46=)32. 
24=(3/4)(32)
24=24