Question 401587
Let {{{a}}} = Ann's age now
Let {{{b}}} = Bill's age now
{{{a + 4}}} = Ann's age in 4 years
{{{b + 4}}} = Bill's age in 4 years
given:
(1) {{{a = (7/10)*b}}}
(2) {{{a + 4 = (8/11)*(b + 4)}}}
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(1) {{{a = (7/10)*b}}}
and,
(2) {{{a + 4 = (8/11)*(b + 4)}}}
Multiply both sides by {{{11}}}
(2) {{{11a + 44 = 8b + 32}}}
Substitute (1) into (2)
(2) {{{11*(7/10)*b + 44 = 8b + 32}}}
(2) {{{77b + 440 = 80b + 320}}}
(2) {{{3b = 120}}}
(2) {{{b = 40}}}
Bill is 40 now
check answer:
From (1),
(1) {{{a = (7/10)*40}}}
(1) {{{a = 28}}}
And, frm (2),
(2) {{{28 + 4 = (8/11)*(40 + 4)}}}
(2) {{{32 = (8/11)*(40 + 4)}}}
(2) {{{32 = 32}}}
OK